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 Fourth Edition Chapter 16 Other RNA Processing Events Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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- Human Cells Processing 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 . | Molecular Biology Fourth Edition Chapter 16 Other RNA Processing Events Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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- Human Cells Processing 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 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 precursors of a single tRNA In bacteria, precursor may contain one or more tRNA 16- Cutting Apart Polycistronic Precursors In processing bacterial RNA that contain more than one tRNA First step is to cut precursor up into fragments with just one tRNA each Cutting between tRNAs in precursors having 2 or more tRNA Cutting between tRNAs and rRNAs in precursors .
