Department of Biology, University of Alabama at Birmingham, Birmingham, AL, USA.
Epigenetics Chromatin. 2022 May 7;15(1):14. doi: 10.1186/s13072-022-00453-8.
In eukaryotes, DNA is packaged into chromatin, which presents significant barriers to transcription. Non-histone chromatin proteins such as the Heterochromatin Protein 1 (HP1) proteins are critical regulators of transcription, contributing to gene regulation through a variety of molecular mechanisms. HP1 proteins are highly conserved, and many eukaryotic genomes contain multiple HP1 genes. Given the presence of multiple HP1 family members within a genome, HP1 proteins can have unique as well as shared functions. Here, we review the mechanisms by which HP1 proteins contribute to the regulation of transcription. Focusing on the Drosophila melanogaster HP1 proteins, we examine the role of these proteins in regulating the transcription of genes, transposable elements, and piRNA clusters. In D. melanogaster, as in other species, HP1 proteins can act as transcriptional repressors and activators. The available data reveal that the precise impact of HP1 proteins on gene expression is highly context dependent, on the specific HP1 protein involved, on its protein partners present, and on the specific chromatin context the interaction occurs in. As a group, HP1 proteins utilize a variety of mechanisms to contribute to transcriptional regulation, including both transcriptional (i.e. chromatin-based) and post-transcriptional (i.e. RNA-based) processes. Despite extensive studies of this important protein family, open questions regarding their functions in gene regulation remain, specifically regarding the role of hetero- versus homodimerization and post-translational modifications of HP1 proteins.
在真核生物中，DNA 被包装成染色质，这对转录有很大的阻碍。非组蛋白染色质蛋白，如异染色质蛋白 1（HP1）蛋白，是转录的关键调节剂，通过多种分子机制参与基因调控。HP1 蛋白高度保守，许多真核生物基因组包含多个 HP1 基因。鉴于基因组中存在多个 HP1 家族成员，HP1 蛋白可以具有独特的和共享的功能。在这里，我们回顾了 HP1 蛋白在转录调控中的作用机制。我们聚焦于黑腹果蝇的 HP1 蛋白，研究这些蛋白在调节基因、转座元件和 piRNA 簇转录中的作用。在黑腹果蝇中，与其他物种一样，HP1 蛋白可以作为转录抑制剂和激活剂。现有的数据表明，HP1 蛋白对基因表达的精确影响高度依赖于特定的 HP1 蛋白、其存在的蛋白伴侣以及相互作用发生的特定染色质环境。作为一个整体，HP1 蛋白利用多种机制来参与转录调控，包括转录（即基于染色质）和转录后（即基于 RNA）过程。尽管对这个重要的蛋白家族进行了广泛的研究，但关于它们在基因调控中的作用仍存在悬而未决的问题，特别是关于异二聚体和 HP1 蛋白的翻译后修饰的作用。
