L19 Gene regulation in eukaryotes

L19 Gene regulation in eukaryotes - Gene regulation in...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Gene regulation in eukaryotes 1 Last Time ✤ Overview of eukaryotic transcription Features of an eukaryotic gene Chromatin remodeling and gene regulation processing ✤ ✤ ✤ RNA ✤ Splicing CAP and PolyA tail modifications 2 ✤ Gene regulation in eukaryotes ✤ Proteins that affect gene transcription: Transcription Factors ✤ Classes (types) Anatomy of a transcription factor How specific transcription factors work ✤ ✤ ✤ Post transcriptional regulation: mRNA stability ✤ The role of the Poly A tail RNA interference (RNAi) 3 ✤ Many ways to regulate gene expression DNA packaging Transcription RNA processing Translation Post-translation Fig 15.1 4 Transcription factors DNA binding proteins that affect the ability of RNAP to begin transcription http://www.embl-grenoble.fr/groups/dna/t.gif 5 Two major categories of TFs ✤ ✤ General transcription factors Specific (‘regulatory’) transcription factors General TFs Specific TFs regulatory sequence core promoter 6 Specific transcription factors 1. 2. 7 Combinatorial control of gene expression ✤ ✤ ✤ Presence or functionality of Activators Presence or functionality of Repressors Modification of Activators and Repressors affect their function ✤ Chromatin condensation level 8 Anatomy of a transcription factor domains = regions of the protein with specific function http://blogs.totalpda.co.uk/wp-content/uploads/2007/10/laptop.jpg 9 Secondary structures in proteins β pleated sheet Amino acid subunits α helix 10 Classic motifs in TFs helix turn helix helix loop helix loop c re g o helix DNA-protein interaction is specific for a given sequence 11 re c he lix lix e h . turn og .h eli x Classic motifs in TFs Zinc finger Leucine zipper Zipper holds two TFs together (dimer) 12 Dimers ✤ ✤ Homodimer - two of the same protein put together Heterodimer - two different proteins put together TF TF homodimer 13 How specific transcription factors work ✤ Control RNAP (indirectly) ✤ Through interaction with TFIID interaction with Mediator ✤Through 14 Specific transcription factors interact with TFIID Activator Repressor 15 Specific transcription factors interact with Mediator Activator Repressor A R 16 Ways specific TF function can be modulated binding of effector molecule protein - protein interaction modification of TF 17 Example - glucocorticoid receptor Steroid hormones act to change gene expression Receptors are modified upon binding, travel to nucleus Control gene expression 18 Post-transcriptional regulation transcript stability conferred by the Poly A tail RNAi controls degradation of transcripts Fig 15.1 19 Not all transcripts are created equal some have short ½ lives some have very long ½ lives Length of polyA tail determines stability http://www.steve.gb.com/images/science/mrna_poly_a_tail.png 20 RNA destroying RNA? RNAi gene in plant genome cloned gene with own promoter inserted transcription occurs from both promoters - dsRNA 21 Fire and Mello (Nobel Prize 2006) RNAi No message - no protein! 22 RNAi is a common form of gene regulation in eukaryotes ✤ Benefits ✤ Precise, sequence specific post-transcriptional gene silencing Protection against certain viruses ✤ ✤ Protection against proliferation of transposons, ‘jumping genes’ 23 Summary ✤ Transcription factors (general or specific) can influence transcription initiation of RNAP ✤ TFs have domains that allow them to associate with DNA or interact with other proteins Specific TFs interact with TFIID or Mediator to control RNAP activity ✤ ✤ mRNA stability is an important contributor to overall mRNA concentration. ✤ The length of the PolyA tail can influence ½ life. RNAi can selectively degrade specific transcripts to reduce or eliminate expression 24 Ungraded problems ✤ ✤ ✤ Check out Chapter 15: S1, S4 and S5 Try Chapter 15: C2-C6, C8, C9, C28, C29, C32 Try Chapter 15: E5 25 Next Time Translation http://genome.imim.es/courses/Madrid04/exercises/ensembl/images/ribosome.jpg 26 ...
View Full Document

This note was uploaded on 03/29/2009 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas.

Ask a homework question - tutors are online