Browsing by Subject "Utp14"
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Item The role of Bud23 in the biogenesis of the small ribosomal subunit in Saccharomyces cerevisiae(2009-08) White, Joshua Paul, 1977-; Johnson, Arlen W.; Stevens, Scott W.Ribosomes are the cellular structures responsible for the synthesis of protein in all branches of life. All ribosomes are made from a large and small subunit that in turn are composed of protein and RNA. The synthesis of eukaryotic ribosomes is a complex process involving more than 200 factors and spans three cellular compartments: the nucleolus, the nucloplasm, and the cytoplasm. The precise function of most of these ribosome biogenesis factors remains unknown. The RNA component of ribosomes is in part processed from a large RNA transcript that yields most of the RNA present in mature ribosomes. Part of the maturation process involves modification of this ribosomal RNA as processing is carried out. Recent work constructing protein interaction networks in Saccharomyces cerevisiae suggested the methyltransferase Bud23 was involved in ribosome biogenesis (1). This thesis describes my work to characterize Bud23 and place it within the ribosome biogenesis pathway. Bud23 is a SAM methyltransferase important for the proper biogenesis of the small ribosomal subunit. Here I will demonstrate that Bud23 methylates G1575 of the small subunit ribosomal RNA (SSU rRNA), and its absence delays export of the SSU rRNA from the nucleolas, and the nucleus, and results in the delayed maturation of the SSU rRNA. Finally, I will show that Bud23 function is connected to small subunit processome factor Utp14 through identification of a Utp14 mutant that suppresses the bud23[Delta] deletion phenotype.Item Utp14 recruits and activates the RNA helicase Dhr1 to undock U3 snoRNA from the pre-ribosome(2016-05) Zhu, Jieyi; Johnson, Arlen W.; Stevens, ScottIn eukaryotic ribosome biogenesis, U3 snoRNA base-pairs with the pre-rRNA to promote its processing. However, U3 must be removed to allow folding of the central pseudoknot, a key feature of the small subunit. Previously, my work contributed to showing that the DEAH/RHA RNA helicase Dhr1 dislodges U3 from the pre-rRNA. DHR1 can be linked to UTP14, encoding an essential protein of the pre-ribosome, through genetic interactions with the rRNA methyltransferase Bud23. Here, I report that Utp14 regulates Dhr1. Mutations within a discrete region of Utp14 reduced its interaction with Dhr1 that correlated with reduced function of Utp14. These mutants accumulated Dhr1 and U3 in a pre-40S particle, mimicking a helicase inactive Dhr1 mutant. This similarity in the phenotypes led us to propose that Utp14 activates Dhr1. Indeed, Utp14 formed a complex with Dhr1 and stimulated its unwinding activity in vitro. Moreover, the utp14 mutants that mimicked a catalytically inactive dhr1 mutant in vivo showed reduced stimulation of unwinding activity in vitro. Dhr1 binding to the pre-ribosome was substantially reduced only when both Utp14 and Bud23 are depleted. Thus, Utp14 is bifunctional; together with Bud23 it is needed for stable interaction of Dhr1 with the pre-ribosome and Utp14 activates Dhr1 to dislodge U3.