Dr. Ranjit Gulvady's Talk

Sep 21, 2017 - 17:00

Sep 21, 2017 - 18:00

Rm. No. 118 Ground floor Chemical Engg. Dept.

Seminars

Dr. Ranjit Gulvady National University of Singapore

Abstract: Bacterial DNA is assembled within the cell with the help of a class of proteins called the Nucleoid Associated Proteins (NAPs). The Histone-like Nucleoid Structuring Protein or H-NS has been shown to be one of the major NAPs that assists in the silencing of potentially virulent genes. While a lot of knowledge on H-NS has been obtained via biochemical studies the molecular mechanisms behind its gene silencing function are not as well studied. Here I shall present the results we obtained with our biophysical study on the H-NS protein. To begin with DNA sequence-dependent H-NS binding was investigated. The 10 bp high-affinity H-NS nucleation site of the proU gene was the primary sequence of interest. The experiments - done using the magnetic tweezer - showed that H-NS has a particularly strong affinity towards the nucleation sites in comparison to similarly designed control sequences in agreement with previous studies. In order to gain a better understanding of the mechanism employed by H-NS in DNA binding the role of the H-NS linker that connects the C and N-terminal was investigated. Point mutations on the linker resulted in a sharp decrease in the binding affinity in comparison to wt H-NS suggesting a charge-dependent mechanism for DNA-binding. In our final study H-NS-DNA binding experiments were done with a longer DNA where the two proU nucleation sites were placed apart from one another. These experiments revealed that H-NS initially prefers binding to the two nucleation sites before undergoing local spreading along the DNA to completely cover it. Taken together these results strengthen our understanding of H-NS-DNA binding and offer a potential mechanism by which H-NS carries out its function of gene silencing.Bio: Dr. Ranjit Gulvady did his Bachelors in Physics from St Xaviers Kolkata. He did his Masters in Physics from IIT-Bombay and his Master’s thesis titled ‘A study of the behaviour of self-propelled particles under the influence of a shearing stress was in the Dept. of Chemical Engineering in Prof Mahesh’s lab. He did his PhD at the National University of Singapore in the field of single-molecule biophysics (in the lab of Prof. Yan Jie). He used various single molecule techniques like magnetic tweezers optical tweezers and Atomic force microscopy (AFM) to study DNA-protein interactions. His talk today will be on one such protein called H-NS which has been the focus of his thesis work.