Replication time of interspersed repetitive DNA sequences in hamsters

Abstract

The replication time of 34 hamster genomic DNA segments containing interspersed repeat sequences was determined by probing the cloned segments with nick-translated early- and late-replicating hamster DNA. One-third of these cloned families replicated early, one-third replicated late, and one-third replicated without temporal bias. 19 different inserts from these clones along with the SINE, Alu, and the LINE, A36Fc, were used to probe Southern blots of early- and late-replicating hamster or human DNA. We report long interspersed repeats, LINEs, are selectively partitioned into late-replicating DNA and are often concertedly hypomethylated, while short interspersed repeats, SINEs, are selectively partitioned into early-replicating DNA. For some interspersed repeat families, this partitioning is complete or almost complete. The CCGG frequency is very low in late-replicating DNA. The mammalian chromosome's pattern of early-replicating R-bands and late-replicating G-bands reflects a differential distribution of LINEs and SINEs.