Study Of Histone H3.3 And Transcription Factor DE2F1 In Drosophila

This thesis consists of two parts of work. The first part is studying on"Regulation of the Expression of Histone H3.3 by Differential Polyadenylation". Previously we have shown that the 3'untranslated regions (UTRs) of the replacement histone genes H3.3A and H3.3B of Drosophila melanogaster differ in their nucleotide sequences and have different polyadenylation sites. To understand their functional relevance, which might explain the presence and evolutionary conservation of 2 different H3.3 genes, green flourescent protein (GFP) constructs with different 3'UTR sections were studied by the expression of GFP as a marker protein. Here we show that the polyadenylation signals modify the cell-specific translation of the histone replacement variants in testes and ovaries. The H3.3A gene may be required to provide postmeiotic histone H3.3 in the male germ line in transition to chromatin packaging in sperm.The second part of work is studying on"A Maternal Effect Mutation of the dE2F1 Gene in Drosophila". The E2F transcription factors are key regulators in cell cycle regulation. In Drosophila, two E2F family members (dE2F1 and dE2F2) have been identified. The dE2F1 gene encodes three transcripts (dE2F1-PA, dE2F1-PB and dE2F1-PC). The three dE2F1 transcripts show temporal and spatial specificities in development. We recovered a novel Drosophila mutant dE2F1TF, induced by the insertion of a transposon into the 5'-UTR, in which dE2F1-PB is knocked out. Genetic analysis of this mutant reveals that the homozygotes are viable, but the offspring embryos of homozygous females are lethal irrespective of the genotype of the embryos. Hence this mutation induces a maternal effect of dE2F1-PB on the early embryonic development. The syncytial blastoderm is delayed, displaying an abnormal asynchrony of the cell cycles and abnormal nuclei localization. RT-PCR documents that dE2F1-PB, like dE2F1-PC, has a tissue-specific expression pattern, while dE2F1-PA is universally expressed. RT-PCR analysis does not reveal any differences in the expression of some genes relevant for early embryonic development or involved in cell cycle regulation. We conclude that the dE2F1 protein is involved in the control of the synchrony, speed...