Structural And Functional Study Of Proteins Involved In The Regulation Of Gene Expression

A variety of important biological events are strictly regulated, such as cell growth, DNA repair and protein ubiquitination. These events are closely involved in the regulation of gene expression that requires the participation of a number of proteins and protein complexes. Here, several proteins that are involved in the regulation of gene expression were studied. Solution structures of these proteins were determined by NMR spectrometer and their functions were explored. This dissertation is divided into five parts.1. YEATS domain, as a novel conserved domain family, was discovered in a variety of eukaryotic species ranging from yeast to human. Taf14 YEATS domain adopts a global fold of an elongatedβ-sandwich. Structural comparison indicated Taf14 YEATS domain differs significantly from Yaf9 YEATS domain in a few aspects, which may indicate different structural classes of YEATS domain family. Experiments in vivo indicate that Taf14 YEATS domain is critical for inhibiting cell growth under stress conditions. In addition, the C-terminus of Taf14 is responsible for its interaction with Sth1, which is an essential component of the RSC complex. All these data suggest Taf14 is involved in transcriptional regulation of Saccharomyces cerevisiae and the YEATS domain of Taf14 might play a negative role in cell growth.2. Rap1 which contains a BRCT domain on the N-terminus performs a few important roles in Saccharomyces cerevisiae, such as telomere replication, activation of glycolytic and ribosomal protein genes. Solution structure of Rap1 BRCT domain was determined by spectrometer. Structural comparison indicated it is similar to structures of other BRCT domains. Meanwhile, there is difference between them. These features reveal a new BRCT domain fold.3. Urm1 is an ubiquitin like protein. Solution structure of Urm1 from trypanosome brucei was determined by spectrometer. Structural comparison indicated it has common structural features of ubiquitin family. Meanwhile its structure is similar to that of MoaD. These results indicate Urm1 is a unique molecular fossil which reveals evolutionary progress of ubiquitin like protein family.4. SAMP1 and SAMP2 were recently discovered as ubiquitin like proteins. NMR expereiment indicated SAMP1 and SAMP2 both have two kinds of conformations, the folded and the disordered conformations, in low salt. However, they both retained only the folded conformation in high salt. Meanwhile, SAMP1 was revealed to be able to interact with PanA (proteasome-activating nucleotidase A) and PanB (proteasome-activating nucleotidase B), suggesting that SAMP1 might be involved in the protein degradation pathway mediated by ubiquitin. This project is completed by three persons (Shanhui Liao, Kai Fan and Wen Zhang) and I am responsible for determination of solution structure and analysis of NMR data.5. In fission yeast, all three states of H4K20me are catalyzed by Set9. Pdp1 is recently discovered as a new Set9 regulator. Pdp1 PWWP domain was revealed to simultaneously bind H4K20me3 and non-specific DNA. Structural comparison revealed Pdp1 PWWP domain has common structural features of PWWP domain family. Western blot result indicated mutations of residues bingding non-specific DNA resulted in decrease of H4K20me2/3. This project is completed by two persons (Yu Qiu and Wen Zhang).