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A map of histone variants and potential phosphorylation sites. Known amino acid sequences (Sullivan et al. 2000) were used to create linear representations of selected histone heteromorphs in the H1, H2A, and H2B histone classes. Conserved regions are shaded yellow, variant regions are in gray, and phosphorylation sites are in green (see text). The locations of selected amino acids are indicated by symbols: +, basic amino acid; ^, hydroxyamino acid; /, proline; |, tyrosine; –, all other amino acids.
Source publication
Histone variants illuminate the behavior of chromatin through their unique structures and patterns of postsynthetic modification. This review examines the literature on heteromorphous histone structures in chromatin, structures that are primary targets for histone kinases and phosphatases in vivo. Special attention is paid to certain well-studied e...
Citations
... It is believed that the protamine-DNA binding dynamic relies primarily on passive electrostatic interaction with the argininerich binding domains (Gou et al. 2020). However, it was shown that PTMs of protamines, especially phosphorylation plays an additional role (Pirhonen et al. 1994b, Green 2001, Seligman et al. 2004. Moritz et al. found that these PTM sites seemed to be conserved within species but can vary between (Moritz et al. 2021 (preprint)). ...
In brief:
Protamines package and shield the paternal DNA in the sperm nucleus and have been studied in many mouse models over decades. This review recapitulates and updates our knowledge about protamines and reveals a surprising complexity in protamine function and their interactions with other sperm nuclear proteins.
Abstract:
The packaging and safeguarding of paternal DNA in the sperm cell nucleus is a critical feature of proper sperm function. Histones cannot mediate the necessary hypercondensation and shielding of chromatin required for motility and transit through the reproductive tracts. Paternal chromatin is therefore reorganized and ultimately packaged by protamines. In most mammalian species, one protamine is present in mature sperm (PRM1). In rodents and primates among others, however, mature sperm contain a second protamine (PRM2). Unlike PRM1, PRM2 is cleaved at its N-terminal end. Although protamines have been studied for decades due to their role in chromatin hypercondensation and involvement in male infertility, key aspects of their function are still unclear. This review updates and integrates our knowledge of protamines and their function based on lessons learned from mouse models and starts to answer open questions. The combined insights from recent work reveal that indeed both protamines are crucial for the production of functional sperm and indicate that the two protamines perform distinct functions beyond simple DNA compaction. Loss of one allele of PRM1 leads to subfertility whereas heterozygous loss of PRM2 does not. Unprocessed PRM2 seems to play a distinct role related to the eviction of intermediate DNA-bound proteins and the incorporation of both protamines into chromatin. For PRM1, on the other hand, heterozygous loss leads to strongly reduced sperm motility as the main phenotype, indicating that PRM1 might be important for processes ensuring correct motility, apart from DNA compaction.
... H2A and H2B transcript variants have a different structure in the N-terminal chain of the transcripts (Frank et al. 2003). TH2B is a testis-specific transcript variant of the H2B histone, which has differences in the structure of three phosphorylation sites (Ser 12, Thr 23 and Thr 34) (Green 2001;Monardes et al. 2005). As a result there are different combinatorial interactions between serine and threonine residues which could be a reason for the specific pattern of acetylation and methylation (Rousseaux et al. 2005). ...
The main role of sperm is the delivery of the paternal genome into the oocyte during fertilisation. However, several lines of evidence have indicated that mammalian spermatozoa contribute more than just their DNA, namely, they also deliver a large range of RNA molecules. Microarray analysis has revealed a complex population of 3000 different kinds of messenger RNA that are delivered to oocytes by sperm and ejaculated spermatozoa are estimated to contain about 0.015 pg of total RNA. Some of the transcripts encode proteins crucial for early embryo development. Messenger RNAs from sperm also help to protect the paternal genes, which have an integral role soon after fertilisation. The molecular participation of the oocyte during fertilisation is well understood but the function of the sperm in this process remains unclear. During spermatogenesis the structure of the male haploid genome is permanently modified. Transition proteins (TNPs), protamines (PRMs) and histones (HILS-spermatid specific linker histone) play a unique role in spermatid chromatin compaction. In this review, the structure and role of sperm RNA as well as chromatin organisation during spermatogenesis are discussed.
... Interestingly, in addition to canonical H2A, H2A.Xand H2A.Z-like proteins, plants exhibit a special class of H2A isoforms that have an extended C-terminus comprising SPKK motifs (31,32) [according to the recently published unified phylogeny-based nomenclature for histone variants: H2A.W (33)]. This kind of motif (more general T/SPXK) is also present in many subtypes of the linker histone H1 and in sea urchin sperm-specific H2B, and it is a known target site for phosphorylation (34). This class of H2A proteins has been shown to protect $16 bp more linker DNA from micrococcal nuclease (MNase) digestion than chicken erythrocyte H2A (35). ...
... A similar situation is found in the sea urchin egg-specific histone variant cleavage stage H2A. Here, C-terminal phosphorylation occurs upon fertilization, possibly leading to chromatin decondensation, which in turn could facilitate chromatin assembly during replication (34). Recently, the histones of bdelloid rotifers, freshwater invertebrates that are highly resistant to ionizing radiation and desiccation (37), were analysed (38). ...
In eukaryotes, DNA is organized together with histones and non-histone proteins into a highly complex nucleoprotein structure called chromatin, with the nucleosome as its monomeric subunit. Various interconnected mechanisms regulate DNA accessibility, including replacement of canonical histones with specialized histone variants. Histone variant incorporation can lead to profound chromatin structure alterations thereby influencing a multitude of biological processes ranging from transcriptional regulation to genome stability. Among core histones, the H2A family exhibits highest sequence divergence, resulting in the largest number of variants known. Strikingly, H2A variants differ mostly in their C-terminus, including the docking domain, strategically placed at the DNA entry/exit site and implicated in interactions with the (H3-H4)(2)-tetramer within the nucleosome and in the L1 loop, the interaction interface of H2A-H2B dimers. Moreover, the acidic patch, important for internucleosomal contacts and higher-order chromatin structure, is altered between different H2A variants. Consequently, H2A variant incorporation has the potential to strongly regulate DNA organization on several levels resulting in meaningful biological output. Here, we review experimental evidence pinpointing towards outstanding roles of these highly variable regions of H2A family members, docking domain, L1 loop and acidic patch, and close by discussing their influence on nucleosome and higher-order chromatin structure and stability.
... These seedlings were then transferred to 6°C chambers (measured at crown level) under 16-hour photoperiod and 220 μmol m -2 s -1 PPFD and sampled at regular intervals. The experimental design was a 4 (genotypes ) × 16 (cold treatment periods: 0, 2, 7, 14, 21, 28, 35, 42, 49, 56, 63, 77, 84, 91 and 98 days) factorial in a randomized complete block design with three replicates. ...
... It accumulates late in spermatogenesis and displaces or augments the germ cell histones to stabilize the highly condensed chromatin. It is hypothesized to play a role in global chromatin reorganization and accessibility of histone variant regions [35]. Protamine could also be involved in the epigenetic regulation of the Vrn-A1 locus as it has also been postulated that maintenance of an active chromatin state at Vrn1 is the basis for epigenetic memory of vernalization in cereals [36]. ...
To identify the genes involved in the development of low temperature (LT) tolerance in hexaploid wheat, we examined the global changes in expression in response to cold of the 55,052 potentially unique genes represented in the Affymetrix Wheat Genome microarray. We compared the expression of genes in winter-habit (winter Norstar and winter Manitou) and spring-habit (spring Manitou and spring Norstar)) cultivars, wherein the locus for the vernalization gene Vrn-A1 was swapped between the parental winter Norstar and spring Manitou in the derived near-isogenic lines winter Manitou and spring Norstar. Global expression of genes in the crowns of 3-leaf stage plants cold-acclimated at 6°C for 0, 2, 14, 21, 38, 42, 56 and 70 days was examined.
Analysis of variance of gene expression separated the samples by genetic background and by the developmental stage before or after vernalization saturation was reached. Using gene-specific ANOVA we identified 12,901 genes (at p < 0.001) that change in expression with respect to both genotype and the duration of cold-treatment. We examined in more detail a subset of these genes (2,771) where expression was highly influenced by the interaction between these two main factors. Functional assignments using GO annotations showed that genes involved in transport, oxidation-reduction, and stress response were highly represented. Clustering based on the pattern of transcript accumulation identified genes that were up or down-regulated by cold-treatment. Our data indicate that the cold-sensitive lines can up-regulate known cold-responsive genes comparable to that of cold-hardy lines. The levels of expression of these genes were highly influenced by the initial rate and the duration of the gene's response to cold. We show that the Vrn-A1 locus controls the duration of gene expression but not its initial rate of response to cold treatment. Furthermore, we provide evidence that Ta.Vrn-A1 and Ta.Vrt1 originally hypothesized to encode for the same gene showed different patterns of expression and therefore are distinct.
This study provides novel insight into the underlying mechanisms that regulate the expression of cold-responsive genes in wheat. The results support the developmental model of LT tolerance gene regulation and demonstrate the complex genotype by environment interactions that determine LT adaptation in winter annual cereals.
... In the past decade, a large number of enzymes have been identified that post-translationally modify histones, introducing chemical modifications, some of which are associated with gene activation and others with repression. The N-terminal tails of the individual histone subunits are prominent targets for modifications, which can alter the higherorder structure of chromatin and influence recruitment of effector molecules (2)(3)(4). Modifications can also occur within the globular histone core (5), affecting binding of DNA to the nucleosome lateral surface, and interactions with nucleosome remodeling complexes that control the mobility of nucleosomes on DNA (6). ...
DNA methylation is deficient in a histone deacetylase 1 (HDA1) mutant (hda-1) strain of Neurospora crassa with inactivated histone deacetylase 1. Difference two-dimensional (2D) gels identified the primary histone deacetylase 1 target as histone H2B. Acetylation was identified by LC-MS/MS at five different lysines in wild-type H2B and at 11 lysines in hda-1 H2B, suggesting Neurospora H2B is a complex combination of different acetylated species. Individual 2D gel spots were shifted by single lysine acetylations. FTICR MS-observed methylation ladders identify an ensemble of 20-25 or more modified forms for each 2D gel spot. Twelve different lysines or arginines were methylated in H2B from the wild type or hda-1; only two were in the N-terminal tail. Arginines were modified by monomethylation, dimethylation, or deimination. H2B from wild-type and hda-1 ensembles may thus differ by acetylation at multiple sites, and by additional modifications. Combined with asymmetry-generated diversity in H2B structural states in nucleosome core particles, the extensive modifications identified here can create substantial histone-generated structural diversity in nucleosome core particles.
... Similar H2As in wheat protect an additional 16 bp of linker DNA from nuclease treatment compared with canonical H2A nucleosomes 110 . These oligopeptides might help stabilize quiescent chromatin in seeds but they become rapidly phosphorylated during germination, perhaps destabilizing the linker DNA interaction 111 . ...
... Sperm histones have poorly understood properties. Sea urchins package sperm DNA in nucleosomes using histone H2B and H1 variants with reversibly phosphorylated minorgroove-binding motifs, rather than using protamines 111 . These histones are proteolysed during pronuclear decondensation 139 and replaced with maternal cleavage-stage histones 88 (see the figure). ...
Histones wrap DNA to form nucleosome particles that compact eukaryotic genomes. Variant histones have evolved crucial roles in chromosome segregation, transcriptional regulation, DNA repair, sperm packaging and other processes. 'Universal' histone variants emerged early in eukaryotic evolution and were later displaced for bulk packaging roles by the canonical histones (H2A, H2B, H3 and H4), the synthesis of which is coupled to DNA replication. Further specializations of histone variants have evolved in some lineages to perform additional tasks. Differences among histone variants in their stability, DNA wrapping, specialized domains that regulate access to DNA, and post-translational modifications, underlie the diverse functions that histones have acquired in evolution.
... Histone H1 has exhibited superiority over the histone sub-types in transfection efficiency (Breeuwer and Goldfarb 1990). Moreover, sea urchin sperm histone H1 (Sp H1) holds great potential due to its specialized DNA condensing properties that derive from its biological role during spermatogenesis and early embryogenesis (Poccia and Green 1992, Green et al. 1995, Green 2001. The present study incorporates Sp H1-pDNA complexes for the purpose of enhancing DNA uptake and gene activation. ...
This study investigated the stability and transfection efficiency of plasmid DNA (pDNA) and sea urchin sperm histone H1 (Sp H1) complexes embedded in albumin microsphere formulations. Sp H1 increased the stability and transfection efficiency of pDNA, while providing a favourable sustained pDNA release profile. Encapsulating Sp H1-complexed pDNA into albumin microspheres further protected the pDNA from physical stress and heparin treatment. When compared with free pDNA encapsulated in albumin microspheres, the Sp H1-pDNA microsphere formulations exhibited decreased hydrophilicity, slower pDNA release profiles, protection against heparin-induced degradation of embedded pDNA and increased stability against physical stress. These results indicate that complex formation of pDNA with Sp H1 facilitates intracellular DNA transfer and that albumin microspheres-Sp H1-pDNA gene delivery formulations are suitable for controlled-release delivery of pDNA while offering protection of the pDNA from degradation and maintaining pDNA biological activity.
... Protein kinases make up a large superfamily of related enzymes, with subdivision into protein serine/ threonine kinases, protein tyrosine kinases, and atypical kinases on the basis of substrate specificity (Hunter, 2000). Phosphorylation plays a central role in chromatin remodeling during meiosis in spermiogenesis (Green, 2001). The Src family of tyrosine kinases regulates proliferation, survival, differentiation, and motility, with eight members in mammalian cells: Src, Yes, Fyn, Hck, Fgr, Lyn, Lek, and Blk. ...
Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review.
... Protein kinases make up a large superfamily of related enzymes, with subdivision into protein serine/ threonine kinases, protein tyrosine kinases, and atypical kinases on the basis of substrate specificity (Hunter, 2000). Phosphorylation plays a central role in chromatin remodeling during meiosis in spermiogenesis (Green, 2001). The Src family of tyrosine kinases regulates proliferation, survival, differentiation, and motility, with eight members in mammalian cells: Src, Yes, Fyn, Hck, Fgr, Lyn, Lek, and Blk. ...
In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation.
... In sea urchins, a maternal kinase phosphorylates sperm-specific histones. This is thought to weaken the sperm histones' attachment to sperm DNA, causing chromatin relaxation (Green and Poccia, 1985; reviewed in Green, 2001). A candidate for the maternal kinase is Cdk2, because it colocalizes with the male pronucleus after fertilization (Schnackenberg and Marzluff, 2002; reviewed in Imschenetzky et al., 2003). ...
The transition from mature oocyte to developing embryo requires a coordinated series of events, collectively known as egg activation. Egg activation includes changes to egg coverings to prevent polyspermy, release of oocyte meiotic arrest, generation of haploid female and male pronuclei, changes in maternal mRNAs and protein populations, and cytoskeletal rearrangements. In many animals, egg activation is triggered by fertilization, which increases intracellular calcium within the oocyte and thereby regulates molecular events of egg activation. In other animals, fertilization-independent external signals, including mechanical stimulation of eggs and/or changes in ionic milieu, trigger activation. Recent studies have clarified the upstream portion of pathways leading to eggshell changes and cell cycle resumption and have identified activation-induced changes in maternal mRNA and protein profiles that can identify molecular players in the downstream events of egg activation. We review signals that trigger activation and how they link to subsequent molecular events of egg activation.
