טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentZilpa Tal
SubjectStructure Function Analysis of Isoform B of the Sef Gene
DepartmentDepartment of Biology
Supervisor Professor Dina Ron


Abstract

        In this work we have made an attempt to study the structure and function relationship of hSef-b product. The newly identified modulator Sef is involved in regulation of signaling pathways triggered by various receptor tyrosine kinases (RTKs). Receptor tyrosine kinases (RTK) control a multitude of biological processes and are therefore subjected to multiple levels of regulation .Sef was first identified as a specific antagonist of fibroblast growth factor (FGF) signaling in zebrafish and subsequently in mouse and human. The Sef gen encodes several isoforms that are generated via an alternative mechanism (designated hSef-a to hSef-d). While hSef-a was found to be located at the cell surface, the hSef-b variant is a cytosolic protein. Both hSef-a and hSef-b differ only over a short stretch of amino-acid residues; they display overlapping but also distinct biological activities. Human Sef-b has ten unique residues in its N-terminus; all the extracellular residues of hSef-a are intracellular in hSef-b. In this study we tried to determine whether the structural and/or the subcellular localization differences between hSef-a and hSef-b contribute to hSef-b function. To address this question, several deletion mutants of hSef-b were designed. Our preliminary results showed that the 10 unique amino acids of hSef-b don’t affect hSef-b inhibitory activity on FGF signaling and on it’s subcellular localization. Similarly, deleting the identical part of hSef-a and hSef-b, which is extracellular in hSef-a and intracellular in hSef-b, didn’t influence hSef-b inhibitory activity on FGF signaling and didn’t affect its subcellular localization. Our results suggest that hSef-b N-terminal region, including the transmembrane domain, doesn’t contribute to its inhibitory activity on the signaling pathway of Ras/MAPK in HEK 293E3 cells.