Sumoylation of the novel protein hRIP beta is involved in replication protein a deposition in PML nuclear bodies

Abstract

Replication protein A (R-PA) 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 alpha has been identified as a carrier molecule of RPA into the nucleus. In this study, human RPAinteracting protein alpha (hRIP alpha) and five novel splice isoforms (named hRIP alpha, hRIP beta, hRIP gamma, hRIP delta 1, hRIP delta 2, and hRIP delta 3 according to the lengths of their encoding peptides) were cloned. Among hRIP isoforms, hRIP(x and hRIP beta were found to be the major splice isoforms and to show different subcellular localizations. While hRIP alpha localized to the cytoplasm, hRIP beta was found in the PML nuclear body. Modification of hRIP beta by sumoylation was found to be required for localization to the PML nuclear body. The results of the present work demonstrate that hRIP beta transports RPA into the PML nuclear body and releases RPA upon UV irradiation. hRIP beta thus plays an important role in RPA deposition in PML nuclear bodies and thereby supplements RPA for DNA metabolism.