Sumoylation of the Novel Protein hRIPβ Is Involved in Replication Protein A Deposition in PML Nuclear Bodies

Abstract

Replication protein A (RPA) is a single-stranded-DNA-binding protein composed of three subunits with molecular masses of 70, 32, and 14 kDa. The protein is involved in multiple processes of eukaryotic DNA metabolism, including DNA replication, repair, and recombination. In Xenopus, Xenopus RPA-interacting protein α has been identified as a carrier molecule of RPA into the nucleus. In this study, human RPA-interacting protein α (hRIPα) and five novel splice isoforms (named hRIPα, hRIPβ, hRIPγ, hRIPδ1, hRIPδ2, and hRIPδ3 according to the lengths of their encoding peptides) were cloned. Among hRIP isoforms, hRIPα and hRIPβ were found to be the major splice isoforms and to show different subcellular localizations. While hRIPα localized to the cytoplasm, hRIPβ was found in the PML nuclear body. Modification of hRIPβ by sumoylation was found to be required for localization to the PML nuclear body. The results of the present work demonstrate that hRIPβ transports RPA into the PML nuclear body and releases RPA upon UV irradiation. hRIPβ thus plays an important role in RPA deposition in PML nuclear bodies and thereby supplements RPA for DNA metabolism.

ACKNOWLEDGMENTS

We especially thank B. Stillman for providing anti-RPA antibody and M. S. Wold for providing RPA p70 clones.

This work was supported in part by grants from the National Research Laboratory Program of the Korea Institute of Science and Technology Evaluation and Planning (KISTEP) and from the Korea Science and Engineering Foundation (KOSEF) through the Protein Network Research Center at Yonsei University.