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Locating the chromatin modifying factor Suppressor of Variegation 3-8 in Drosophila melanogaster Carvalho, Anna-Bella


This study is part of a project whose goal is to identify and then sequence the chromatin modifying gene Su(var)3-8. Chromatin structure is considered to play a significant role in gene expression. In order to better understand this role, we have undertaken a project to characterize one gene suspected of affecting chromatin structure, Su(var)3-8. The first approach taken was to tag the gene with a known sequence - the P element transposon. Mutations of Su(var)3-8 created by P element mutagenesis were tested to determine whether P elements were inserted in the gene. Remobilization of the P element by a cross that introduced transposase was used to detect reverted suppressors, under the supposition that precise excision of a mutation-causing P element would revert the gene to wild-type state. Southern blotting using radioactively labelled complete P element to probe digested genomic DNA was used to detect partial (immobile) remnants of P elements. Recessive lethal mutations containing P elements inserted in the region near Su(var)3-8 were tested for complementation to determine whether those P elements were inserted into the 3-8 locus. As no P-tagged alleles were discovered, Su(var)3-8 was then localized with the intention of delimiting the potential area to a few genes, allowing for direct testing of putative genes via plasmid rescue. Su(var)3-8 was localized genetically using recombination mapping with the genes cross-veinless and stubbloid, situated on the chromosomal arm 3R and near where previous studies placed Su(var)3-8 (53.5±0.9 ). 3-8 was localized cytologically by complementation to various recessive lethal chromosomal deficiencies also determined to be in the vicinity. It was not possible to localize the area sufficiently to allow for direct testing of open reading frames. 128 putative genes are located in the 1645Kb within which Su(var)3-8 appears to be located.

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