Fold recognition insights into function of herpes ICP4 protein.

ICP4 is an important factor regulating the life cycle of HSV1. This conserved protein has several molecular functions, including activation of expression of viral late gene transcripts and inhibition of immediate early genes. Although ICP4 and its Alphaherpesvirinae homologs (eg.: IE62 of VZV) have been subjects of various molecular studies, a complete view of their molecular function is lacking. Here we present the results of fold recognition and molecular modelling of ICP4 functional domains. The performed state-of-the-art bioinformatic fold recognition analysis identified a dual helix-turn-helix motif as a binding module of repressor activities (so called region 2 domain). The mapping of distant homology identified that a segment responsible for activation of late gene promoters (region 4) exhibits folding of uracil DNA glycosylase (UDG), but seems to be a non-functional homolog of UDG. Potential implications of the results are discussed.