Large T antigen, polyomaviridae (IPR016392)

Short name: Lg_T_Ag_polyomavir

Overlapping homologous superfamilies

Family relationships



The group of polyomaviruses is formed by the homonymous murine virus (Py) as well as other representative members such as the simian virus 40 (SV40) and the human BK and JC viruses [PMID: 8824775]. Their large T antigen (T-ag) protein binds to and activates DNA replication from the origin of DNA replication (ori). Insofar as is known, the T-ag binds to the origin first as a monomer to its pentanucleotide recognition element. The monomers are then thought to assemble into hexamers and double hexamers, which constitute the form that is active in initiation of DNA replication. When bound to the ori, T-ag double hexamers encircle DNA [PMID: 17139255]. T-ag is a multidomain protein that contains an N-terminal J domain, which mediates protein interactions (see PDOC00553, IPR001623), a central origin-binding domain (OBD), and a C-terminal superfamily 3 helicase domain (see PDOC51206, IPR010932) [PMID: 16611889].

This group represents a large T antigen, Polyomaviridae type.

The oncogenic large tumour antigen (LTag) is a protein found in polyomaviruses which is essential for viral DNA replication [PMID: 1847451]. LTag contains three domains, an N-terminal DnaJ domain which mediates protein interactions (IPR001623), a domain which binds the origin of DNA replication (IPR003133), and a C-terminal helicase domain. Replication is intitated by LTag assembling at the origin as a double hexamer that distorts and melts the origin DNA [PMID: 1847451, PMID: 2539565]. During elongation LTag acts as a helicase that unwinds duplex DNA at the replication forks [PMID: 3025851].

GO terms

Biological Process

GO:0006260 DNA replication

Molecular Function

GO:0005524 ATP binding
GO:0003688 DNA replication origin binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.