Abstract:
Aided by sensitive sequence profile searches we identify a novel conserved domain in the Nterminal
regions of the SWI2/SNF2 proteins typified by HIP116 and Rad5p (hence HIP116,
Rad5p N-terminal domain: HIRAN domain). We show that the HIRAN domain is found as a
standalone protein in several bacteria and prophages, or fused to other catalytic domains, such
as a nuclease of the restriction endonuclease fold and TDP1-like DNA phosphoesterases, in the
eukaryotes. Based on a network of contextual connections in the form of domain architectures,
conserved gene neighborhoods and functional interactions we predict that the HIRAN domain is
likely to function as a DNA-binding domain that probably recognizes features associated with
damaged DNA or stalled replication forks. It might thus act as a sensor to initiate a damaged DNA
checkpoint and engage different DNA repair and chromatin remodeling or modifying activities to
these sites. In evolutionary terms, the fusion of the HIRAN domain, and the functionally
analogous Rad18 Zn-finger and the PARP-type Zn-finger to SWI2/SNF2 ATPases appears to
have been a notable factor for recruiting these ATPases for chromatin modification and
remodeling in the context of DNA repair.