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BioMed Research International
Volume 2013 (2013), Article ID 854745, 9 pages
Research Article

Structural and Sequence Similarities of Hydra Xeroderma Pigmentosum A Protein to Human Homolog Suggest Early Evolution and Conservation

1Division of Animal Sciences, Agharkar Research Institute, G. G. Agarkar Road, Pune 411 004, India
2Department of Zoology, University of Pune, Ganeshkhind, Pune 411 007, India

Received 15 April 2013; Accepted 31 July 2013

Academic Editor: Sanford I. Bernstein

Copyright © 2013 Apurva Barve et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Xeroderma pigmentosum group A (XPA) is a protein that binds to damaged DNA, verifies presence of a lesion, and recruits other proteins of the nucleotide excision repair (NER) pathway to the site. Though its homologs from yeast, Drosophila, humans, and so forth are well studied, XPA has not so far been reported from protozoa and lower animal phyla. Hydra is a fresh-water cnidarian with a remarkable capacity for regeneration and apparent lack of organismal ageing. Cnidarians are among the first metazoa with a defined body axis, tissue grade organisation, and nervous system. We report here for the first time presence of XPA gene in hydra. Putative protein sequence of hydra XPA contains nuclear localization signal and bears the zinc-finger motif. It contains two conserved Pfam domains and various characterized features of XPA proteins like regions for binding to excision repair cross-complementing protein-1 (ERCC1) and replication protein A 70 kDa subunit (RPA70) proteins. Hydra XPA shows a high degree of similarity with vertebrate homologs and clusters with deuterostomes in phylogenetic analysis. Homology modelling corroborates the very close similarity between hydra and human XPA. The protein thus most likely functions in hydra in the same manner as in other animals, indicating that it arose early in evolution and has been conserved across animal phyla.