Histone chaperones regulate histone exchange during transcription
Hye-Jin Kim1, Ja-Hwan Seol1, Jeung-Whan Han1, Hong-Duk Youn2 and Eun-Jung Cho1
1 College of Pharmacy, Sungkyunkwan University, Suwon, Gyeonggi-do, Republic of Korea
2 Department of Biochemistry and Molecular Biology, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
To whom correspondence should be addressed
Eun-Jung Cho, College of Pharmacy, Sungkyunkwan University, 300 Chencheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Republic of Korea. Tel.: +82 31 290 7781; Fax +82 31 292 8800
Transcription by RNA polymerase II is accompanied by dynamic changes in chromatin, including the eviction/deposition of nucleosomes or the covalent modification of histone subunits. This study examined the role of the histone H3/H4 chaperones, Asf1 and HIR, in histone mobility during transcription, with particular focus on the histone exchange pathway, using a dual histone expression system. The results showed that the exchange of H3/H4 normally occurs during transcription by the histone chaperones. Both Asf1 and HIR are important for histone deposition but have a different effect on histone exchange. While Asf1 mediated incorporation of external H3/H4 and renewal of pre-existing histones, HIR opposed it. The balance of two opposing activities might be an important mechanism for determining current chromatin states.