Initiator protein NS1

UniProtKB accession:  P03134

Grouped By:  Matching UniProtKB accession

UniProtKB description:  Multifunctional protein which displays endonuclease and helicase activities required for initiating and directing viral DNA replication (PubMed:12050365). Also plays a role in viral packaging and transactivation of several promoters (PubMed:7636987). Binds site-specifically to 2-3 approximate tandem copies of the tetranucleotide 5'TGGT3' within the origins of replication (Ori), unwinds this hairpin region and nicks one DNA strand thereby initiating the rolling circle replication (RCR) (PubMed:17898054, PubMed:12050365, PubMed:9349487). Cooperatively binds Ori with host PIF and probably other host factors, which activate the nickase function of NS1 (PubMed:11435581, PubMed:12050365). Becomes covalently attached to the 5' end of the nick and provides a 3'OH for priming DNA synthesis (PubMed:12050365). The helicase activity unwinds DNA in a 3'-5' direction on the longer strand (PubMed:12050365). Participates in the transcriptional regulation of several promoters including the viral p38 promoter that regulates the expression of VP1 and VP2 transcripts (PubMed:7636987, PubMed:8551622). Inhibits the host cell cycle during the G1/S transition, the S-phase, and the G2/M transition (PubMed:9188601, PubMed:11602746). These arrests may provide essential cellular factors for viral DNA replication. Promotes apoptosis in host cell (PubMed:21295324).