3'- to 5' DNA unwinding by TIP49b proteins.
TIP49b (reptin) is an essential eukaryotic AAA+ ATPase involved in a variety of cellular processes, such as chromatin remodeling during double-strand break repair, transcriptional regulation, control of cell proliferation and small nucleolar RNA biogenesis. How it acts at the molecular level remains largely unknown. In the present study, we show that both human TIP49b and its yeast orthologue, Rvb2p, cooperatively bind single-stranded DNA as monomers. Binding stimulates a slow ATPase activity and supports a 3'- to 5' DNA unwinding activity that requires a 3'-protruding tail >or= 30 nucleotides. The data obtained indicate that DNA unwinding of 3'- to 5' junctions is also constrained by the length of flanking duplex DNA. By contrast, TIP49b hexamers were found to be inactive for ATP hydrolysis and DNA unwinding, suggesting that, in cells, protein factors that remain unknown might be required to recycle these into an active form.
Papin
Christophe
C
Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse, France.
Humbert
Odile
O
Kalashnikova
Anna
A
Eckert
Kelvin
K
Morera
Solange
S
Käs
Emmanuel
E
Grigoriev
Mikhail
M
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D006801:Humans; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D002352:Carrier Proteins; D004277:DNA, Single-Stranded; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; D000251:Adenosine Triphosphatases; C428199:RVB2 protein, S cerevisiae; D000074183:ATPases Associated with Diverse Cellular Activities; D004265:DNA Helicases; C122079:RUVBL2 protein, human