UNIVERSITY OF MALTA
RESEARCH SEMINARS
Abstract form
Title: Transcription factor binding to, and promoter activity of, the defensin
gene
Presenter: Pierre Schembri-Wismayer
Contact address: Room 006, Anatomy & Cell Biology Dept., University of Malta
Tel: 2340 2795
Fax: 21319527
Email: pierre.schembri-wismayer@um.edu.mt
Presentation date: 7th March 2005
Abstract
(approximately 200-250 words)
Leukaemia is a disease of disordered differentiation and proliferation. Genetic anomalies
associated with leukaemia include chromosomal translocations associated with anomalous
transcription factors or signal transduction molecules, up regulation of transcription factors
and oncogenes and more recently discovered mutations in receptor-associated tyrosine
kinases. All these offer options for targeted therapy.
Defensin - a neutrophil granule protein gene expressed at a common point of differentiation
block in certain leakaemias was studied. Analysis of defensin gene expression was a method
to identify the transcription factors involved in this stage of leukocyte differentiation.
Methods used to study the immediate upstream sequences were – DNAse1 footprinting,
Electrophoretic Mobility Shift Assays (EMSA) and transfections with reporter genes.
Pu.1, GABP, C/EBPs, AML and Myb were transcription factors found to be important in the
regulation of defensin gene expression.
Studies using the promyelocytic leukaemia cell line NB4 showed the changes in
transcriptional activity for different deletion mutants of the defensin promoter, identifying a
minimal promoter and identifying site important for differentiation-induced up-regulation of
gene transcription.
The importance of the binding sites for GABP, Myb and C/EBP in particular for regulation
of this promoter activity was also demonstrated using transfections in NB4 myeloid and
HeLa epithelial cells.
Both reporter gene studies as well as EMSA indicated previously unreported functional
interactions between the components of the tetrameric GABP transcription factor and other
transcription factors.
This has led on to further studies aimed at defining these interactions and their relation to
myeloid differentiation.