在细胞周期中,姐妹染色单体内聚系链姐妹染色单体从S期到中期-后期过渡,并确保将染色单体准确分离到子细胞中。N-末端乙酰化是真核生物中最普遍的蛋白质共价修饰之一,并且由N-末端乙酰转移酶(NAT)家族介导。Naa50(也称为San)先前已被证明在后生动物的姐妹染色单体内聚力中发挥作用。然而,Naa50有助于内聚的机制尚不清楚。这里,我们发现HeLa细胞中Naa50的耗竭削弱了粘附素与其正调节素之间的相互作用,并导致S期的内聚缺陷,与Naa50在凝聚力建立中的作用一致。引人注目的是,NatA的共同消耗,与Naa50物理相互作用的异二聚体NAT复合物,挽救姐妹染色单体内聚缺陷和由Naa50耗尽引起的有丝分裂停滞,表明NatA和Naa50在凝聚力中起拮抗作用。纯化的重组NatA和Naa50在体外不影响彼此的NAT活性,因为NatA和Naa50表现出不同的底物特异性,我们建议它们修饰不同的效应子,并以相反的方式调节姐妹染色单体的内聚力。
During the cell cycle, sister-chromatid cohesion tethers sister chromatids together from S phase to the metaphase-anaphase transition and ensures accurate segregation of chromatids into daughter cells. N-terminal acetylation is one of the most prevalent protein covalent modifications in eukaryotes and is mediated by a family of N-terminal acetyltransferases (NAT). Naa50 (also called San) has previously been shown to play a role in sister-chromatid cohesion in metazoans. The mechanism by which Naa50 contributes to cohesion is not understood however. Here, we show that depletion of Naa50 in HeLa cells weakens the interaction between cohesin and its positive regulator sororin and causes cohesion defects in S phase, consistent with a role of Naa50 in cohesion establishment. Strikingly, co-depletion of NatA, a heterodimeric NAT complex that physically interacts with Naa50, rescues the sister-chromatid cohesion defects and the resulting mitotic arrest caused by Naa50 depletion, indicating that NatA and Naa50 play antagonistic roles in cohesion. Purified recombinant NatA and Naa50 do not affect each other\'s NAT activity in vitro Because NatA and Naa50 exhibit distinct substrate specificity, we propose that they modify different effectors and regulate sister-chromatid cohesion in opposing ways.