REGULATION OF VARIANT HUMAN HISTONE MRNAS

我们克隆了一个变异型人H_2B核心(GL105)组蛋白基因和一个变异型H1连接物(CI110)组蛋白基因。在HeLa细胞周期中，H_2B组蛋白基因表达差异调节的可选择的mRNAs。H_2B基因编码500个核苷酸的复制依赖的信使核糖核酸和2300个核苷酸的HHC89组成性表达的信使核糖核酸。细胞周期调节的mRNA的3‘末端紧跟在大多数组蛋白mRNAs典型的连接的二联体对称区之后，而结构性表达的HHC289 mRNA有一个1798个核苷酸的非翻译拖尾，它包含相同的连接的二联体对称性区域，但是多腺化的。我们的结果表明，复制依赖和结构性表达的组蛋白mRNAs可以由同一基因编码，并表明选择性3‘末端加工是细胞在细胞周期和分化开始时调节不同组蛋白合成的主要调控水平。当进行Northern印迹分析时，我们观察到第二个变异体H_2B基因的2300个核苷酸的表达。H1组蛋白基因和H_2B变异体一样，包含一个连接的二联体对称性的3‘区和一个多加烯化序列。这一基因的调控目前正在调查中。这些研究的长期目标是了解在不同生物条件下调控不同组蛋白基因RNA转录产物表达和加工的细胞机制和信号。这些研究将阐述变异组蛋白基因的表达在多大程度上受到细胞生长状态的调节。我们还将研究特定的核苷酸序列在不同的人组蛋白mRNAs的调节和替代处理中所起的作用。在细胞增殖状态的变化过程中，将分析不同的人类组蛋白基因的转录后调节。这些结果将为真核基因表达、生长调控、分化和致癌提供更多的洞察力。

We have isolated a variant human H2B core (GL105) histone gene and a variant Hl linker (CI110) histone cDNA. The H2B histone gene expresses alternative mRNAs regulated differentially during the HeLa cell cycle.. The H2B gene encodes both a 500 nt replication-dependent mRNA and a 2300 NT HHC89 constitutively expressed mRNA. The 3' end of the cell cycle regulated mRNA terminates immediately following the region of hyphenated dyad symmetry typical of most histone mRNAs, whereas the constitutively expressed HHC289 mRNA has a 1798 nt non-translated trailer that contains the same region of hyphenated dyad symmetry but is polyadenylated. Our results demonstrate that replication-dependent and constitutively expressed histone mRNAs can be encoded by the same gene and indicate that alternative 3' end processing is a major level of regulation by which cells can modulate the synthesis of variant histone proteins during the cell cycle and at the onset of differentiation. When Northern blot analysis was carried out we observed the 2300 nt expression of a second variant H2B gene. The H1 histone gene, like the H2B variant, contains a 3' region of hyphenated dyad symmetry and a polyaddenylation sequence. The regulation of this gene is now under investigation. The long-range objective of these studies is to understand the cellular mechanisms and signals, that modulate the expression and processing of RNA transcripts from the variant histone genes under different biological conditions. These studies will address the extent to which the expression of variant histone genes is modulated by the growth state of the cell. We will also examine the role specific nucleotide sequences play in the regulation and alternative processing of variant human histone mRNAs. The post-transcriptional regulation of variant human histone genes will be analyzed during changes in the proliferative state of the cell. These results will provide additional insight into eukaryotic gene expression growth regulation, differentiation, and carcinogenesis.