Dr. Suman Kumar Dhar has been awarded the 2012 Shanti Swarup Bhatnagar Award for his contributions to the understanding of the unique characteristics of DNA replication and cell cycle regulation in two medically important pathogens, Plasmodium falciparum and Helicobacter pylori.
Dr. Dhar’s studies involve finding key regulators in DNA replication processes that could be potential targets for therapy. His group has identified two targets, PfGyrase for P. falciparum and HpDnaB helicase for H. pylori. One of the crucial observations is the co-localization of H. pylori single stranded DNA binding protein (SSB) and HpDnaB helicase in sharp, distinct foci in exponentially growing H. pylori cells, but spread over large areas in dormant coccoid form providing evidence of multiple roles of SSB, central to bacterial physiology and pathogenesis. Further, he showed that the N‑terminus of HpDnaB is involved in switching between strong DNA binding and weak DNA binding activity that may be central to the loading and translocation functions of DnaB helicases.
Dr Dhar is also studying the control of both organeller apicoplast DNA and nuclear DNA replication in P. falciparum. He has functionally characterized key molecules that are essential for nuclear DNA replication. A bacterial type II topoisomerase, gyrase (A and B), and single-stranded DNA binding protein (SSB) homolog, essential for apicoplast DNA replication have been identified. Gyrase is absent in the human host thus making P. falciparum gyrase an attractive drug candidate. Interestingly, ciprofloxacin and coumermycin, the gyrase-specific drugs kill Plasmodium parasites in vitro. His group has also identified a putative origin recognition complex subunit in P. falciparum (PfORC5) that co-immunoprecipitates with proliferating cell nuclear antigen (PCNA) during early-to-mid trophozoite stage replicating parasites, while separate from PCNA at the non-replicating late schizont stage. This distinct colocalization of PCNA and ORC in Plasmodium is not common in higher eukaryotes.
These original contributions from Dr. Dhar’s laboratory not only further our understanding of the basic biology of these parasites but also have the potential to manage diseases like gastric ulcer, gastric adenocarcinomas (caused by Helicobacter pylori) and human malaria (caused by Plasmodium falciparum).
Dr. Suman Kumar Dhar is an Associate Professor at the Special Center for Molecular Medicine, Jawaharlal Nehru University, New Delhi. More details are available at http://www.jnu.ac.in/main.asp?sendval=scmmFacultyProfile.