4月22日,，科技期刊《生殖生物學》（Biology of Reproduction）以“Histone H2A Has a Novel Variant in Fish Oocytes”為題在線發(fā)表了中科院水生生物所淡水生態(tài)與生物技術國家重點實驗室桂建芳研究組的研究成果,。
桂建芳研究組以銀鯽為材料，在魚類卵母細胞中發(fā)現(xiàn)了一種新的核心組蛋白H2A變體,。他們在篩選到一個卵母細胞核心組蛋白H2A變體cDNA的基礎上,，首先分析確定了其卵母細胞特異表達的模式，接著觀察到該蛋白在卵子發(fā)生過程中的磷酸化修飾作用,。由于它是一個卵母細胞特異的H2A新變體,，該變體基因被定名為h2af1o (H2A histone family, member 1, oocyte specific)。為了解這個新變體在核小體中的結合動力學特征,，他們還從銀鯽中克隆出另一個遍在的h2afx,，并進一步采用體外過表達和FRAP實驗方法比較分析了這兩個組蛋白在染色質中的動態(tài)交換差異。有意思的是,，H2af1o在核小體中比遍在的H2afx有更高的運動性,，并且，與遍在的H2afx相比,，H2af1o有更緊結合的C端和更弱結合的N端,。這些結果表明，魚類卵母細胞中有一個新的H2A變體,，其更為游離的N端可能提供了更多的修飾位點,，并能輕微降低核小體的穩(wěn)定性，而其緊密結合的C端保證了核小體的中心區(qū)域的穩(wěn)定,。這些發(fā)現(xiàn)意味著H2af1o可能在魚類卵子發(fā)生,、卵母細胞成熟和早期卵裂中有改變?nèi)旧|特性的能力,。
該研究得到國家基礎研究973計劃等項目的資助，主要由博士研究生吳南等完成,。據(jù)論文通訊作者桂建芳研究員介紹,，組蛋白是核小體的重要成分，在基因表達模式的傳輸和核小體運動性的表觀遺傳調(diào)節(jié)中起了重要作用,；組蛋白也存在許多變體，且這些變體在特定的細胞或特定的細胞周期階段發(fā)揮了至關重要的轉錄調(diào)控作用,。由于卵母細胞是高度特化的細胞,，過去雖找到了一些卵母細胞特異的連接組蛋白，但迄今還未鑒定出卵母細胞特異的核心組蛋白,。因此,，這一新的魚類卵母細胞特異的核心組蛋白H2A變體的發(fā)現(xiàn)對進一步研究魚類卵子發(fā)生和卵母細胞成熟過程中的調(diào)控機制有重要意義。（生物谷Bioon.com）
生物谷推薦原始出處：
Biology of Reproduction,，doi：10.1095/biolreprod.108.074955,，Nan Wu，Jian-Fang Gui
Histone H2A Has a Novel Variant in Fish Oocytes
Nan Wu , Hua-Mei Yue , Bo Chen , and Jian-Fang Gui *
Abstract
Histone variants and their modifications play significant roles in many cellular processes. In this study, we have identified and characterized a histone H2A variant h2af1o in fish, and revealed its oocyte-specific expression pattern during oogenesis and embryogenesis. Moreover, a post-translational modification of H2af1o was observed, and the modification was demonstrated to result from the phosphorylation during oocyte maturation. To understand the binding dynamics of the novel core histone variant H2af1o in nucleosomes, we cloned another ubiquitous gibel carp h2afx as the conventional histone control, and investigated the dynamic exchange difference in chromatin by fluorescence recovery after photobleaching (FRAP). Significantly, H2af1o was revealed to confer relatively higher mobility in nucleosomes than that of ubiquitous H2afx. And, in comparison with ubiquitous H2afx, H2af1o has a tightly binding C terminus and a weak binding N terminus. The current data indicate that fish oocytes have a novel H2A variant that slightly destabilizes nucleosomes by protruding its N-terminal tail to a large extent, and stabilizes core particle by its tightly binding C-terminal tail. Our findings suggest that H2af1o might have the intrinsic ability to modify chromatin properties during fish oogenesis, oocyte maturation and early cleavage.
