Semester of Graduation
Master of Science (MS)
HMGB proteins are eukaryotic, chromatin-associated proteins that play roles in both DNA dynamics and transcription regulation. Hmo1p is an HMGB protein in Saccharomyces cerevisiae that behaves somewhat like a hybrid between mammalian HMGB proteins and the metazoan linker histone H1. mTORC1, a protein complex containing the Tor1p kinase and a major regulator of cellular growth, is inhibited by both rapamycin and stress. It has also been shown to not only associate with Hmo1p at various gene promoters, but also regulate the HMO1 gene itself through direct binding. In this study, the Hmo1p-mTORC1 relationship was further investigated through two questions: 1) Does the transcription factor Sfp1p play a role in relaying mTORC1’s signal to the HMO1 promoter, and 2) Is the reduction in HMO1 transcripts during stress dependent on mTORC1? Gene expression analyses revealed that Sfp1p is not required for normal HMO1 transcription; however, it does appear to play a role in transmitting the mTORC1 stress signal to the promoter, as transcripts are only significantly decreased during stress when Sfp1p is present. Survival tests revealed that Sfp1p might be hindering the cell’s ability to repair DNA double-strand breaks, as there is a slight increase in cell survival during double-strand break-induction when Sfp1p is knocked-out; however, there is some uncertainty as to whether this is Hmo1p-related. Chromatin Immunoprecipitation techniques were then used to demonstrate that RNA polymerase II is evicted from the HMO1 gene over the course of one hour during stress when Tor1p is knocked-out. This same phenomenon had previously been shown in wild-type cells; however, HMO1 transcripts are only attenuated in wild-type cells, and not when Tor1p is knocked-out. This suggests that mTORC1 is responsible for the reduction of HMO1 mRNA during stress. We propose the possibility that mTORC1 is participating in active mRNA degradation at the HMO1 gene, and that transcription-inhibition techniques can be utilized to confirm this.
Smith, Mathew Damien, "Investigating the Role of TORC1 and the Transcription Factor Sfp1p in the Regulation of HMO1 Gene in Saccharomyces cerevisiae" (2020). LSU Master's Theses. 5070.