DYNAMICS OF HUMAN REPLICATION PROTEIN-A SUBUNIT DISTRIBUTION AND PARTITIONING IN THE CELL-CYCLE

Human replication protein A (RPA) is a three-subunit protein complex i nvolved in DNA replication, repair, and recombination. To gain insight into the dynamics of subunit assembly, we examined the subcellular di stribution of RPA subunits (p70, p34, and p11) during the cell cycle. All three subunits colocalized in G1 and S phases, showing a diffuse n uclear distribution in G1 but a dot-like nuclear pattern in S phase. D uring S phase, the subunits showed a pattern reminiscent of the replic ation granules/factories described by others as sites of replication m achinery. In metaphase, p70 preferentially associated with the spindle poles, p34 was found on chromosomes, and pll remained in the cytoplas m, In telophase, p70 and p34 appeared in the forming daughter nuclei; pll remained in the cytoplasm until G1. Among the three subunits only p34 was associated with the nuclear matrix and this association persis ted throughout the cell cycle. We conclude that (i) RPA complex assemb ly is differentially regulated, (ii) the replication machinery may be anchored to the nuclear matrix, and (iii) RPA subunits partition durin g mitosis and sort into daughter nuclei by different routes. (C) 1996 academic Press, Inc.