The identification and characterisation of a novel Apoptotic Gene,Snama, in drosophila melanogaster
Date
2006-11-15T13:01:51Z
Authors
Mather, Arshad Saleh
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Abstract
SNAMA is the Drosophila melanogaster homologue of a group of proteins that are
known to bind p53 and the retinoblastoma protein (Rb). This multi domain protein
consists of a conserved N-terminal domain called Domain With No Name (DWNN),
a zinc finger, a cysteine rich RING finger-like domain, a probable p53 binding
region, and a glutamic acid-rich and lysine-rich region. These associated domains
indicate that SNAMA plays an important regulatory role in the cell and may function
in RNA processing and in apoptosis.
The DWNN domain was first identified in Cytotoxic T-cell resistant Chinese hamster
ovary (CHO) cells using promoter trap mutagenesis to screen for genes involved in
apoptosis. Subsequently, this domain was identified in other eukaryotic organisms
including animals and plants.
The SNAMA transcriptional unit consists of 9 exons and 8 introns that code for a
1231 amino acid protein with the 76 residue N-terminal DWNN domain. The DWNN
domain has a 23.5% sequence identity to the ubiquitin protein and a predicted folded
structure similar to ubiquitin. Western blots identified multiple bands indicative of
ubiquitin tagged proteins. Taken together this suggests a role in the ubiquitin pathway
either as an ubiquitin domain protein or the DWNN domain of SNAMA tagging other
proteins. The cysteine rich RING finger-like domain has a histidine to serine
substitution at the fourth position of the putative RING finger and represents a distinct class of RING finger-like proteins that could have ubiquitin ligase activity.
Northern blot analysis identified a single 4.6 kbp transcript expressed abundantly
throughout development early in embryogenesis but reduced in older embryos and in
adult male and females. SNAMA probably interacts with Dmp53 as a suppressor of
apoptosis or a negative regulator of an activator of apoptosis. It is a vital gene
required for development, as the mutant P-element insertion line in which the Pelement
is inserted in the first intron of SNAMA is lethal when homozygous.
Acridine orange staining of these mutant flies showed a direct correlation between the
presence of SNAMA and apoptosis. An increase in the levels of apoptosis occurred in
embryos with relatively low levels of SNAMA expression. The mode of this action is
either direct, or via other proteins that are involved in the apoptotic pathway.
Description
Student Number : 9105022E -
PhD thesis -
School of Molecular and Cell Biology -
Faculty of Science
Keywords
cell cycle, RNA processing, p53, retinoblastoma protein (Rb), DWNN