The Structural Biology Research Of Yeast SDT1 And CDC73

The 5'-nucleotidases catalyze the dephosphorylation of ribo- and deoxyribonucleoside monophosphates to the corresponding nucleosides. These enzymes can counteract the activity of nucleoside kinases and compete with other enzymes that consume the nucleoside monophosphates, which balance NTP and dNTP pools in cell. SDT1,first found as the deletion inhibitory factor of transcription elongation factor TFIIS in S. cerevisiae, suppresses the damage induced by deletion of TFIIS by overexpression. Here we report the 1.9? crystal structure of the yeast SDT1 complexed with phosphate and magnesium ions. We also present a 1.7 ? crystal structure of D61A variant complexed with the optimal substrate U5P (uridine 5'-monophosphate). The native SDT1 shows a classic HAD enzymes superfamily structure. The D61A variant structure enables us to characterize that the enzyme's specificity for the ribo- form of nucleoside 5'-monophosphate is contributed to Asp-63, Asp-130 and Tyr-193.The yeast Paf1 complex (Paf1C), composed of the proteins Paf1, Cdc73, Ctr9, Leo1, and Rtf1, associates with RNA polymerase II (pol II) from the promoter to the 3′end formation site of mRNA encoding genes. As one component of the first two identified subunits of the Paf1 complex, Cdc73_Yeast (yCdc73) takes part in many transcription related processes including: binding to the RNA polymerase II; recruitment and activation of histone modification factors; communication with other transcriptional activators. The human homolog of yCdc73, also called as parafibromin, is identified as a tumor suppressor linked to breast, renal and gastric cancer. However, the functional mechanism of Cdc73 is not clear until recently. Here, we show the 2.1? crystal structure of the highly conserved C-terminal region of yCdc73. It reveals that Cdc73 appears as a GTPase-like fold. We hope that our found sheds new light on the function modes of cdc73 and Paf1 complex.