Chapter 16 - Other RNA processing events. This chapter includes contents: Ribosomal RNA processing, transfer RNA processing, trans-splicing, RNA editing, posttranscriptional control of gene expression, post-transcriptional control of gene expression: RNA interference. | Molecular Biology Fifth Edition Chapter 16 Other Post-Transcriptional Events Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Other Processing Events In a few organisms, other specialized pre-mRNA processing events occur, such as trans-splicing Most organisms process their rRNAs and tRNAs by more conventional mechanisms Eukaryotes control some of their gene expression by regulating posttranscriptional processes, primarily mRNA degradation 16- Ribosomal RNA Processing rRNA genes of both eukaryotes and bacteria are transcribed as larger precursors must be processed to yield rRNAs of mature size Several different rRNA molecules are embedded in a long, precursor and each must be cut out 16- Eukaryotic rRNA Processing Ribosomal RNAs are made in eukaryotic nucleoli as precursors that must be processed to release mature rRNAs Order of RNAs in the precursor is 18S 28S in all . | Molecular Biology Fifth Edition Chapter 16 Other Post-Transcriptional Events Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Other Processing Events In a few organisms, other specialized pre-mRNA processing events occur, such as trans-splicing Most organisms process their rRNAs and tRNAs by more conventional mechanisms Eukaryotes control some of their gene expression by regulating posttranscriptional processes, primarily mRNA degradation 16- Ribosomal RNA Processing rRNA genes of both eukaryotes and bacteria are transcribed as larger precursors must be processed to yield rRNAs of mature size Several different rRNA molecules are embedded in a long, precursor and each must be cut out 16- Eukaryotic rRNA Processing Ribosomal RNAs are made in eukaryotic nucleoli as precursors that must be processed to release mature rRNAs Order of RNAs in the precursor is 18S 28S in all eukaryotes Exact sizes of the mature rRNAs vary from one species to another 16- Processing scheme of human rRNA precursor 5’-end of 45S precursor RNA is removed to 41S 41S precursor is cut into 2 parts: 20S precursor of 18S 32S precursor of and 28S rRNA 3’-end of 20S precursor removed, yielding mature 18S rRNA 32S precursor is cut to liberate and 28S rRNA and 28S rRNA associate by base-pairing 16- Bacterial rRNA Processing Bacterial rRNA precursors contain tRNA and all 3 rRNA rRNA are released from their precursors by RNase III and RNase E RNase III is the enzyme that performs at least the initial cleavages that separate the individual large rRNAs RNase E is another ribonuclease that is responsible for removing the 5S rRNA from the precursor 16- Processing bacterial rRNA precursors 16- Transfer RNA Processing Transfer RNAs are made in all cells as overly long precursors These must be processed by removing RNA at both ends Nuclei of eukaryotes contain .
