Faculty of Biotechnology, University of Wrocław, 50-383 Wrocław, Poland.
Nucleic Acids Res. 2024 Jul 8;52(12):7112-7128. doi: 10.1093/nar/gkae418.
Streptomyces are soil bacteria with complex life cycle. During sporulation Streptomyces linear chromosomes become highly compacted so that the genetic material fits within limited spore volume. The key players in this process are nucleoid-associated proteins (NAPs). Among them, HU (heat unstable) proteins are the most abundant NAPs in the cell and the most conserved in bacteria. HupS, one of the two HU homologues encoded by the Streptomyces genome, is the best-studied spore-associated NAP. In contrast to other HU homologues, HupS contains a long, C-terminal domain that is extremely rich in lysine repeats (LR domain) similar to eukaryotic histone H2B and mycobacterial HupB protein. Here, we have investigated, whether lysine residues in HupS are posttranslationally modified by reversible lysine acetylation. We have confirmed that Streptomyces venezuelae HupS is acetylated in vivo. We showed that HupS binding to DNA in vitro is controlled by the acetylation. Moreover, we identified that CobB1, one of two Sir2 homologues in Streptomyces, controls HupS acetylation levels in vivo. We demonstrate that the elimination of CobB1 increases HupS mobility, reduces chromosome compaction in spores, and affects spores maturation. Thus, our studies indicate that HupS acetylation affects its function by diminishing DNA binding and disturbing chromosome organization.
链霉菌是一种具有复杂生命周期的土壤细菌。在孢子形成过程中，链霉菌的线性染色体变得高度紧凑，使得遗传物质能够适应有限的孢子体积。在这个过程中起关键作用的是类核相关蛋白（NAPs）。其中，HU（热不稳定）蛋白是细胞中含量最丰富的 NAPs，在细菌中也是最保守的。HupS 是由链霉菌基因组编码的两个 HU 同源物之一，是研究最深入的孢子相关 NAP。与其他 HU 同源物不同，HupS 含有一个长的 C 末端结构域，该结构域富含赖氨酸重复（LR 结构域），类似于真核生物组蛋白 H2B 和分枝杆菌的 HupB 蛋白。在这里，我们研究了 HupS 中的赖氨酸残基是否通过可逆赖氨酸乙酰化进行翻译后修饰。我们证实了链霉菌 venezuelae HupS 在体内发生乙酰化。我们表明，HupS 在体外与 DNA 的结合受乙酰化的控制。此外，我们还鉴定出 CobB1（链霉菌中两种 Sir2 同源物之一）在体内控制 HupS 的乙酰化水平。我们证明消除 CobB1 会增加 HupS 的迁移率，降低孢子中的染色体紧凑度，并影响孢子的成熟。因此，我们的研究表明，HupS 的乙酰化通过减少 DNA 结合和扰乱染色体组织来影响其功能。
