Human RECQ1 and RECQ4 helicases play distinct roles in DNA replication initiation.
Cellular and biochemical studies support a role for all five human RecQ helicases in DNA replication; however, their specific functions during this process are unclear. Here we investigate the in vivo association of the five human RecQ helicases with three well-characterized human replication origins. We show that only RECQ1 (also called RECQL or RECQL1) and RECQ4 (also called RECQL4) associate with replication origins in a cell cycle-regulated fashion in unperturbed cells. RECQ4 is recruited to origins at late G(1), after ORC and MCM complex assembly, while RECQ1 and additional RECQ4 are loaded at origins at the onset of S phase, when licensed origins begin firing. Both proteins are lost from origins after DNA replication initiation, indicating either disassembly or tracking with the newly formed replisome. Nascent-origin DNA synthesis and the frequency of origin firing are reduced after RECQ1 depletion and, to a greater extent, after RECQ4 depletion. Depletion of RECQ1, though not that of RECQ4, also suppresses replication fork rates in otherwise unperturbed cells. These results indicate that RECQ1 and RECQ4 are integral components of the human replication complex and play distinct roles in DNA replication initiation and replication fork progression in vivo.
Thangavel
Saravanabhavan
S
International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy.
Mendoza-Maldonado
Ramiro
R
Tissino
Erika
E
Sidorova
Julia M
JM
Yin
Jinhu
J
Wang
Weidong
W
Monnat
Raymond J
RJ
Falaschi
Arturo
A
Vindigni
Alessandro
A
D002460:Cell Line; D049109:Cell Proliferation; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication; D042522:DNA Replication Timing; D015536:Down-Regulation; D016193:G1 Phase; D006801:Humans; D034921:Lamin Type B / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000378:metabolism; D053484:RecQ Helicases / Q000378:metabolism*; D018741:Replication Origin / Q000235:genetics; D016196:S Phase; D055544:beta-Globins / Q000235:genetics / Q000378:metabolism
D002843:Chromatin; D034921:Lamin Type B; D034741:RNA, Small Interfering; D055544:beta-Globins; D004247:DNA; C506725:RECQL protein, human; C506731:RECQL4 protein, human; D053484:RecQ Helicases