©1998 Timothy G. Standish Hebrews 1:1-2 1God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, 2Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds;

©1998 Timothy G. Standish Transcription From DNA To RNA Timothy G. Standish, Ph. D.

DNA mRNA Transcription Introduction The Central Dogma of Molecular Biology Cell Polypeptide (protein) Translation Ribosome

©1998 Timothy G. Standish RNA Polymerase RNA Polymerase is a spectacular enzyme, functioning in: 1 Recognition of the promoter region 2 Melting of DNA (Helicase + Topisomerase) 3 RNA Priming (Primase) 4 RNA Polymerization 5 Recognition of terminator sequence

©1998 Timothy G. Standish 5’3’ RNA Transcript A “Simple” Gene Protein Coding Region Terminator Sequence Promoter/ Control Region 3’ Untranslated Region Transcription Start Site 5’ Untranslated Region

©1998 Timothy G. Standish Stages of Transcription 1 Initiation 2 Elongation 3 Termination

©1998 Timothy G. Standish Transcription Initiation Proteins called transcription factors bind to the promoter region of a gene If the appropriate transcription factors are present, RNA polymerase binds to form an initiation complex RNA polymerase melts the DNA at the transcription start site Polymerization of RNA begins

©1998 Timothy G. Standish RNA Pol.Initiation Promoter RNA Pol. T. F. 5’ RNA

©1998 Timothy G. Standish RNA Pol.Initiation RNA Pol. T. F. 5’ RNA Promoter T. F.

©1998 Timothy G. Standish Transcription Termination There are two types of termination: Rho dependent requires a protein called Rho, that binds to and slides along the RNA transcript. The terminator sequence slows down the elongation complex, Rho catches up and knocks it off the DNA Rho independent termination depends on both slowing down the elongation complex, and an AT-rich region that destabilizes the elongation complex

©1998 Timothy G. Standish RNA Pol. 5’ RNA Pol. 5’ RNA Termination Rho Independent Terminator

©1998 Timothy G. Standish RNA Pol. 5’ RNA Pol. 5’ RNA Termination Rho Independent Terminator

©1998 Timothy G. Standish RNA Pol. 5’ RNA Termination Rho Dependent Terminator  RNA Pol. 5’ RNA  The terminator sequence slows RNA polymerase

©1998 Timothy G. Standish RNA Pol. 5’ RNA Termination Rho Dependent Terminator  Help, Rho hit me! RNA Pol. 5’ RNA  Rho catches up with RNA polymerase

©1998 Timothy G. Standish RNA Pol. 5’ RNA Termination Rho Dependent Terminator  RNA Pol. 5’ RNA  The elongation complex disintegrates

©1998 Timothy G. Standish Differences Between Transcription In Prokaryotes and Eukaryotes

©1998 Timothy G. Standish 3’ 5’ 3’ Transcription And Translation In Prokaryotes Ribosome 5’ mRNA RNA Pol.

©1998 Timothy G. Standish DNA Cytoplasm Nucleus Eukaryotic Transcription Export G AAAAAA RNA Transcription Nuclear pores G AAAAAA RNA Processing mRNA

©1998 Timothy G. Standish A “Simple” Eukaryotic Gene Terminator Sequence Promoter/ Control Region Transcription Start Site RNA Transcript 5’ Untranslated Region 3’ Untranslated Region Exons Introns 3’5’ Exon 2Exon 3 Int. 2 Exon 1 Int. 1 3’5’ Exon 2Exon 3Exon 1 Int. 2Int. 1

©1998 Timothy G. Standish 3’5’ Exon 2Exon 3 Int. 2 Exon 1 Int. 1 Processing Eukaryotic mRNA Protein Coding Region 3’ Untranslated Region5’ Untranslated Region 3’ AAAAA 3’ Poly A Tail 5’ G 5’ Cap Exon 2 Exon 3Exon 1 Int. 2Int. 1 RNA processing achieves three things:  Removal of introns  Addition of a 5’ cap  Addition of a 3’ tail l This signals the mRNA is ready to move out of the nucleus and may control its lifespan in the cytoplasm

©1998 Timothy G. Standish