Wei-wei Gao, Rong-quan Xiao, Bing-ling Peng, Huan-teng Xu, Hai-feng Shen, Ming-feng Huang, Tao-tao Shi, Jia Yi, Wen-juan Zhang, Xiao-nan Wu, Xiang Gao, Xiang-zhi Lin, Pieter C. Dorrestein, Michael G. Rosenfeld, and Wen Liu

Significance

HSP70 proteins are well known as molecular chaperones involved in protein folding and quality control. Whether they also function in gene transcription on chromatin, and if so, how they are regulated, remains elusive. Here we report that HSP70 can also regulate gene transcription through its association with chromatin, distinct from its “classic” function as a molecular chaperone. The function of HSP70 in gene transcription is subject to regulation of an arginine methylation on a highly conserved residue in HSP70, which modulates the recruitment of a key component in the pre-initiation complex, and thus transcription initiation. The present study reveals an additional, previously overlooked function of HSP70 chaperone proteins, and links arginine methylation of nonhistone proteins to gene transcriptional regulation.

Abstract

Although “histone” methyltransferases and demethylases are well established to regulate transcriptional programs and to use nonhistone proteins as substrates, their possible roles in regulation of heat-shock proteins in the nucleus have not been investigated. Here, we report that a highly conserved arginine residue, R469, in HSP70 (heat-shock protein of 70 kDa) proteins, an evolutionarily conserved protein family of ATP-dependent molecular chaperone, was monomethylated (me1), at least partially, by coactivator-associated arginine methyltransferase 1/protein arginine methyltransferase 4 (CARM1/PRMT4) and demethylated by jumonji-domain–containing 6 (JMJD6), both in vitro and in cultured cells. Functional studies revealed that HSP70 could directly regulate retinoid acid (RA)-induced retinoid acid receptor β2 (RARβ2) gene transcription through its binding to chromatin, with R469me1 being essential in this process. HSP70’s function in gene transcriptional regulation appears to be distinct from its protein chaperon activity. R469me1 was shown to mediate the interaction between HSP70 and TFIIH, which involves in RNA polymerase II phosphorylation and thus transcriptional initiation. Our findings expand the repertoire of nonhistone substrates targeted by PRMT4 and JMJD6, and reveal a new function of HSP70 proteins in gene transcription at the chromatin level aside from its classic role in protein folding and quality control.

See: http://www.pnas.org/content/112/26/E3327.abstract.html?etoc

PNAS June 30, 2015 vol. 112 no. 26 E3327-E3336

Fig. S4.

Cellular localization of HSP70 and its R469-methylated form. (A) HEK293T cells were subjected to immunostaining with anti-HSP70 antibody. HSP70 proteins are shown in green. (B) Cellular fractionation was done in three independent cell lines, HCT116, SW480, and LNCaP, followed by IB with various antibodies as indicated.