10BIS1012013EuKTranscLect10

The gamma and beta phosphates of the gtp are lost as

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Unformatted text preview: nes and Gene Expression, R.L. Rodriguez 18 Capping with Guanylyl Transferase γ P β P α α γ β α P P P γ β P β γ α BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodriguez 19 Sequence of Capping Reaction ­ Step 1: The gamma phosphate of the base at the 5' end of the hnRNA is Step removed by an enzyme called nucleotide phosphohydrolase. removed ­ Step 2: A molecule of GTP condenses with the end of the RNA, catalyzed Step by the enzyme guanylyl transferase. The gamma and beta phosphates of the GTP are lost as PPi during this reaction. The resulting linkage is 5' to the 5'' as indicated in all of the structures shown above. 5 ­ Step 3: The guanine residue of the cap is methylated at the 7 position of Step the base, catalyzed by a methyl transferase and using as a source of methyl groups S-adenosyl methionine (SAM). methyl ­ Step 4: Sometimes, methyl transferase will add methyl groups to the Step 2'-OH of the ribose sugars of the first or second base in the RNA, again using SAM as a methyl donor. These structures are called Cap 1 and Cap 2, respectively. Cap BIS101­001, Spring 2013—Genes and Gene Expression, R.L. Rodrig...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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