Identification and Characterization of a Novel Human Histone H3 Lysine 36-specific Methyltransferase

Xiao-Jian Sun,Ju Wei,Xin-Yan Wu,Ming Hu,Lan Wang,Hai-Hong Wang,Qing-Hua Zhang,Sai-Juan Chen,Qiu-Hua Huang,Zhu Chen

doi:10.1074/jbc.m504012200

Abstract

Histone methylation plays an important role in eukaryotic transcriptional regulation. A number of histone methyltransferases (HMTases) with distinct functions have been identified. The HSPC069/HYPB gene was originally isolated from the human hematopoietic stem/progenitor cells (HSPCs), and it was also identified as a huntingtin interacting protein, implicated in the pathogenesis of Huntington disease (HD). However, its biochemical function is poorly understood. Here we report the structural and functional characterization of the huntingtin interacting protein B (HYPB). 1) The triplicate AWS-SET-PostSET domains mediate a histone H3 lysine 36 specific HMTase activity. 2) A low charged region that is rich in glutamine and proline has been characterized as a novel transcriptional activation domain. The structural features of this region are evolutionarily conserved in vertebrates. 3) Coimmunoprecipitation assays indicate that HYPB protein associates with hyperphosphorylated RNA polymerase II (RNAPII) but not the unphosphorylated form. Furthermore, the RNAPII-association region of HYPB protein has been identified to encompass the C-terminal 142 amino acids. Thus, our results suggest that HYPB HMTase may coordinate histone methylation and transcriptional regulation in mammals and open perspective for the further study of the potential roles of HYPB protein in hematopoiesis and pathogenesis of HD.

Highlights

Nucleosome, the bead-like unit of DNA packaging in eukaryotic cells, consists of DNA wound around a protein core made up of eight histone molecules
Independent studies indicated that the C-terminal region of the encoded protein interacts with Huntington disease (HD) protein huntingtin, and it was named as huntingtin interacting protein B (HYPB), implying its roles in pathogenesis [24, 25]
To investigate whether the low charged region of HYPB protein could function as a transcriptional regulatory domain, different regions of HYPB protein fused with the DNA-binding domain (DBD) of Gal4 protein were examined for their effects on a Gal4 recognition sites-driven luciferase reporter gene (5Gal4-luc; Fig. 4A)

Summary

Introduction

Nucleosome, the bead-like unit of DNA packaging in eukaryotic cells, consists of DNA wound around a protein core made up of eight histone molecules. Not all SET domain-containing proteins possess histone methyltransferase (HMTase)5 activities. We found that HYPB protein possesses a histone H3 lysine 36 (H3-K36) specific HMTase activity.

Results

Conclusion