Investigation of tRNA-derived small RNAs in drosophila melangaster

Abstract

Types of small RNAs considered as crucial players of regulation of gene expression increase gradually in number. Improvements in cloning and sequencing strategies and technologies resulted in identification of tRNA derived small RNAs which are highly expressed in the cell just like other small RNAs such as microRNAs, endosiRNA, and Piwi interacting RNAs. Depending on stress and changing physiological conditions, tRFs are originated from different positions, in different frequency and different tRNAs. However, their functions and the complexes they interact with remain largely unknown. In this thesis study, one of the aims is to characterize tRNA derived small RNAs expressed during embryonic development in Drosophila melanogaster by in-vitro and invivo experiments. This study also aimed to demonstrate the differences between embryonic tRFs and stress induced tRNA derived small RNAs. Lastly, it was aimed to obtain some clues about their biogenesis, mechanism and functions. It was shown that the tRFs expressed in 1-hour and 8-h Drosophila embryos are different from stress induced tRNA derived small RNAs in terms of both position and length. The other important result is that embryonic tRFs are associated with complexes in mRNP and 60S fractions and they are expressed temporally and selectively during Drosophila embryogenesis.