Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

216 Biennial Report 2005-076.1.5.5 In Search of Halophilic bacteria from Natural Sources:Although a lot of work has been done on halophilic organisms, which includes a wide range ofarcheabacteria, a systematic study of the halophilic/ halo-tolerant bacteria is quite scanty in theliterature. In order to undertake a study in this field we have isolated halophilic/ halo-tolerantbacteria from dry fish procured from different places of origin. We have obtained a number of suchbacteria, on which we are working to have an idea of their morphological, biochemical and salttolerance properties. Initial study revealed that the organisms isolated, were mostly gram positivecocci and their salt tolerance levels was upto 3M of NaCl.Sambaran Dey, AK PalBP6.1.5.6 Cell cycle regulation in Leishmania parasites: Regulation of S-phase specificgene expression in Leishmania donovaniThe lack of transcriptional regulation in unicellular protozoa trypanosomatids, many species ofwhich cause a wide range of human diseases, suggests the presence of distinct post-transcriptionalmechanisms to control differential gene expression. In fact, the stability of S-phase specific mR-NAs in these parasites is determined primarily by the presence of the octanucleotide sequence(C/A)AUAGAA(G/A) in the UTRs of the transcripts. We have cloned and characterized themRNA cycling sequence binding proteins from Leishmania donovani (LdCSBP), which specificallybinds to the octanucleotide containing RNA. The LdCSBP protein contains multiple putative functionaldomains including two types of ubiquitin binding domains UBA and CUE, two CCCH-typeZn-finger motifs and a speculative endonuclease domain SMR. The Zn-finger motifs have beenshown to contain the specific RNA binding activity of LdCSBP. Interestingly, the protein is covalentlymodified through ubiquitination. This observation and the occurrence of multiple ubiquitinbinding domains in the protein raise the possibility of regulation of the activity of LdCSBP byubiquitination. (This project is partially funded by DBT, India)Dipankar Bhandari, Partha SahaC&MB6.1.5.7 Cell cycle regulation in Leishmania parasites: Characterization of cyclinsfrom Leishmania donovaniLike in other eucaryotes, cyclins and CRKs (CDK Related Kinases) are essential for the cell cycleprogression in Leishmania. In our laboratory, a cyclin (LdCyc1) and a CRK (LdCRK3) havealready been characterized from Leishmania donovani. Another cyclin molecule (LdCyc2) hasbeen cloned from the same parasite. The full length ORF has been sequenced and the sequence hasbeen submitted to the GenBank. Northern Blot analysis revealed that the mRNA of the LdCyc2gene was expressed maximally 3 hous after an S phase arrest with Hydroxyurea, one cell cycleduration being about 3.5 hours. The mechanism of such periodic expression of the message is beingstudied.Santanu Roy, Partha SahaC&MB