Hoda Moazzen

Date of Award


Degree Type


Degree Name

Master of Science




Dr. Anthony Percival-Smith


The Drosophila HOX transcription factor, Sex Combs Reduced (SCR), is required for determining labial and the first thoracic segmental identity. A Protein Phosphatase 2A holoenzyme assembled with the PP2A-B' regulatory subunit has been proposed to specifically interact with and dephosphorylate SCR homeodomain activating SCR protein activity. To test this hypothesis, a null mutation was created in the PP2A-B' gene, PP2A- B'a, using Flip mediated site-specific recombination. The number of sex comb bristles, salivary gland nuclei and pseudotracheal rows are SCR-dependent and were counted as a measure of SCR activity in vivo. Adults and larvae homozygous for PP2A-B'a showed no decrease in SCR activity. In addition no evidence of functional redundancy of PP2A-B' with other regulatory subunits, Twins (TWS) and Widerborst (WDB) for dephosphorylation and activation of SCR activity was observed suggesting that PP2A has

no role in activation of SCR activity.



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