Core histone N-termini play an essential role in mitotic chromosome condensation

We have studied the role of core histone tails in the assembly of mitotic c hromosomes using Xenopus egg extracts. Incubation of sperm nuclei in the ex tracts led to the formation of mitotic chromosomes, a process we found to b e correlated with phosphorylation of the N-terminal tail of histone H3 at S er10, When the extracts were supplemented with III-depleted oligosomes, the y were not able to assemble chromosomes. Selective elimination of oligosome histone tails by trypsin digestion resulted in a dramatic decrease in thei r ability to inhibit chromosome condensation. The chromosome assembly was a lso inhibited by each of the histone tails with differing efficiency. In ad dition, we found that nucleosomes were recruiting through the flexible hist one tails some chromosome assembly factors, different from topoisomerase II and 13S condensin, These findings demonstrate that histone tails play an e ssential role in chromosome assembly, We also present evidence that the nuc leosomes, through physical association, were able to deplete the extracts f rom the kinase phosphorylating histone H3 at Ser10, suggesting that this ki nase could be important for chromosome condensation.