ESTABLISHING LINKAGE BETWEEN GINS COMPLEX SUB-UNIT Sld5 AND CHECKPOINT PROTEIN Chk2 (loki) USING DROSOPHILA MELANOGASTER AS MODEL ORGANISM

Devadasan, Divya

ESTABLISHING LINKAGE BETWEEN GINS COMPLEX SUB-UNIT Sld5 AND CHECKPOINT PROTEIN Chk2 (loki) USING DROSOPHILA MELANOGASTER AS MODEL ORGANISM

Files

DEVADASAN_ecu_0600M_10708.pdf (9.47 MB)

Date

2012

Authors

Devadasan, Divya

Publisher

East Carolina University

Abstract

Eukaryotic DNA replication is controlled by a number of proteins that ensures the process takes place accurately. GINS, a hetero-tetrameric protein complex is known to be essential for the initiation and progression of eukaryotic DNA replication. The GINS complex constitutes four subunits; Sld5, Psf1, Psf2, Psf3. The Sld5 subunit of GINS is an evolutionarily conserved protein. Previous research from our lab shows that Sld5 is required for normal cell cycle progression and the maintenance of genomic integrity. In addition, the depletion of other GINS sub-units Psf1 and Psf2 by siRNA in human fibroblasts lead to genomic instability and activation of Chk2. Preliminary results in Drosophila show that there are mitotic phase delays in the Sld5 mutant lines compared to wild-type. To further investigate the role of Sld5 in checkpoint signaling, a multifaceted approach is being used. First, Sld5-Chk2 double mutants were generated to check for replication defects and cell cycle progression. The mitotic delay observed in Sld5 mutants were found to be mediated through Chk2. Interestingly enough, the S-phase delay observed in Sld5 mutants did not appear to be mediated through Chk2, though there was an S-phase delay observed endogenously in the loki/loki;Sld5/+ mutants. Evidence of endo-replication defects and differences in the packaging ratio of DNA between wild-type and mutants was investigated in salivary glands. Sld5 mutants showed significantly larger amounts of DNA per nuclei although the nuclei were packaged similar to wild-type. Errors due to under-replication or over-replication can lead to disastrous consequences leading to several genetic diseases like cancer, developmental abnormalities etc. Therefore, analyzing the role of Sld5 in checkpoint regulation is essential for understanding its contribution in the maintenance.