Alternative Title

Regulation of giant by Polycom-Group Proteins




Polycomb Group (PcG) proteins are evolutionarily conserved epigenetic transcriptional regulators that maintain the transcriptional repression of silenced genes. PcG mediated silencing is divided into two phases: initiation and maintenance. During the initiation phase, PcG proteins initially recognize and bind to their target genes. Once PcG proteins are recruited to their target genes, they can maintain transcriptional repression through an unlimited number of cell cycles. Most studies on PcG proteins have been focused on the maintenance phase of PcG silencing, and the molecular mechanisms by which PcG proteins are initially recruited to their target genes remained unknown. Two models have been proposed for the initial recruitment of PcG proteins to their target genes: instructive and responsive models. Instructive model suggests that transcription factors regulate recruitment of PcG proteins to the chromatin of their target genes. On the other hand, the responsive model suggests that recruitment of PcG proteins is dependent on the transcriptional state of the target genes and repressed chromatin is more compatible for the assembly and stable binding of PcG proteins. In order to experimentally test these two models, we examined the recruitment of PcG silencing complexes at a transcriptionally inert giant (gt), the PcG target, transgene in a background in which endogenous gt is transcriptionally active. We demonstrated that PcG proteins do not respond to gttranscriptional state. Furthermore, we provided evidence for the inhibitory effect of the gttranscriptional activator, Caudal (cad), on the recruitment of PcG proteins and proposed that this inhibitory effect is antagonized by the presence of the gtrepressor, Hunchback (Hb).

Degree Date

Fall 12-2019

Document Type


Degree Name



Biological Sciences


Richard S. Jones

Number of Pages