BI256 Lecture Notes - Lecture 7: Pseudouridine, Guanosine, 5.8S Ribosomal Rna
Document Summary
Cleavage of multiple rrnas from a common precursor. Same 3 types of rrna that make up rna: 18s, 28s, 5. 8s: (transfer) trna processing. Base pairing between complementary sequences located in different regions causes each trna molecule to fold into a secondary structure containing hairpin loops. Principle modifications include methylation of bases and sugars and careation of unusual bases such as dihydrouracil, ribothymine, pseudouridine and inosine: (messenger) mrna processing (eukaryotes) Capping, addition of poly(a)tail, and removal of introns. 5" cap: guanosine nucleotide that has been methylated at position 7 of the purine ring and is backward. 5" cap contributes to mrna stability by protecting the molecule from degradation by nucleases that attach rna at the 5" end & exonucleases. Also plays important role in positioning mrna on the ribosome for initiation of translation. Methylated guanosine nucleotide (added shortly after initiation of rna synthesis)
