REGULATION OF VARIANT HUMAN HISTONE MRNAS

我们分离了一个人类H2B核心（GL105）组蛋白变异基因和一个Hl连接子（CI110）组蛋白变异cDNA。H2B组蛋白基因在HeLa细胞周期中表达不同的mrna。H2B基因编码500 nt复制依赖性mRNA和2300 nt HHC89组成性表达mRNA。大多数组蛋白mRNA的典型特征是，细胞周期调节的mRNA的3'端立即终止于连字符对称区域，而组成性表达的HHC289 mRNA有一个1798 nt的非翻译尾部，包含相同的连字符对称区域，但被聚腺苷化。我们的研究结果表明，复制依赖性和组成性表达的组蛋白mrna可以由同一个基因编码，并表明在细胞周期和分化开始时，可选择的3'端加工是细胞调节变异组蛋白合成的主要调控水平。当进行Northern blot分析时，我们观察到第二种H2B基因变体在2300 nt的表达。H1组蛋白基因，像H2B变体一样，包含一个3'的带连字符的双体对称区域和一个多腺苷化序列。这个基因的调控目前正在研究中。这些研究的长期目标是了解细胞机制和信号，在不同的生物学条件下，调节来自变异组蛋白基因的RNA转录物的表达和加工。这些研究将解决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。我们还将研究特定核苷酸序列在人类组蛋白mrna变异的调控和替代加工中所起的作用。变异人类组蛋白基因的转录后调控将在细胞增殖状态的变化中进行分析。这些结果将为真核基因表达、生长调控、分化和癌变提供更多的见解。

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.