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A regula eucariotes
- 1. Regulación de la Expresión Génica en Eucariotes
- 2. Regulación en Eucariotes Complejidad: • Mayor cantidad de DNA •Mayor número de cromosomas •Separación espacial transcripción-traducción •Procesamiento del mRNA •Estabilidad del RNA •Diferenciación celular
- 3. Niveles de Regulación
- 4. Organización de la Cromatina
- 5. Regulación Transcripcional • Factores de • Unión RNA transcripción polymerase II
- 6. • Los potenciadores (Enhancers) contienen secuencias cortas de DNA que puede incluir sitios de unión a factores positivos y negativos.
- 8. • Activador de la transcripción •Acetilación de histonas •Metilación del DNA
- 9. Remodelación del Nucleosoma Alteración del contacto entre proteínas Figure 17-9a Copyright © 2006 Pearson Prentice Hall, Inc.
- 10. Remodelación del Nucleosoma Alteración del DNA alredeor del octámero Figure 17-9b Copyright © 2006 Pearson Prentice Hall, Inc.
- 11. Remodelación del Nucleosoma Remodelación del octámero Figure 17-9c Copyright © 2006 Pearson Prentice Hall, Inc.
- 12. Remodelación del Nucleosoma • La acetiltransferasa (HAT) disminuye la atracción entre las histonas y el DNA • Las desacetilasas (HDACs) revierten este efecto
- 13. Figure 17-10 Copyright © 2006 Pearson Prentice Hall, Inc.
- 14. Ensamblaje del complejo de transcripción basal • TFIID se une a TATA mediante TATA binding protein (TBP)
- 15. Figure 17-11 Copyright © 2006 Pearson Prentice Hall, Inc.
- 16. Los activadores se unen a los potenciadores (enhancers) y a los factores de transcripción Figure 17-13 Copyright © 2006 Pearson Prentice Hall, Inc.
- 17. • Los activadores tienen un dominio de unión al DNA. –Hélice-vuelta-hélice –Dedos de zinc –Cremalleras de leucina
- 18. Hélice – Vuelta - Hélice Figure 17-14 Copyright © 2006 Pearson Prentice Hall, Inc.
- 19. Dedos de Zinc Figure 17-15 Copyright © 2006 Pearson Prentice Hall, Inc.
- 20. Cremalleras de Leucina Figure 17-16 Copyright © 2006 Pearson Prentice Hall, Inc.
- 21. Metilación del DNA • Análisis con enzimas de restricción
- 22. Figure 17-19a Copyright © 2006 Pearson Prentice Hall, Inc.
- 23. Figure 17-19b Copyright © 2006 Pearson Prentice Hall, Inc.
- 24. • metilación expresión génica • Patrones tejido-específicos • 5-azacitidina: hipometilación y cambios en la espresión génica.
- 25. Regulación Postranscripcional • Splicing • 5' cap • 3' poly-A
- 26. Splicing Alternativo Figure 17-23 Copyright © 2006 Pearson Prentice Hall, Inc.
- 27. Degradación del RNA Figure 17-23 Copyright © 2006 Pearson Prentice Hall, Inc.
- 28. Figure 17-25 Copyright © 2006 Pearson Prentice Hall, Inc.
- 29. Regulación Traduccional •Ribosomas •tRNA •Factores de iniciación •Factores de elongación
- 30. Regulación Pos-Traduccional •Corte selectivo de aminoácidos terminales •Acetilación •Adición de: –Grupos fosfato –Grupos carboxilo –Grupos metilo –Hidratos de carbono
Notas del editor
- Figure 17-1 Various levels of regulation that are possible during the expression of the genetic material.
- Figure 17-5 Organization of the promoter regions in several genes expressed in eukaryotic cells, illustrating the variable nature, number, and arrangement of controlling elements.
- Figure 17-8 The SWI/SNF nucleosome remodeling complexes can be directed to specific DNA sites in several ways. (a) Transcription factors, including those with leucine zipper domains can target binding. (b) Histone components of nucleosomes modified by acetylation can serve as SWI/SNF targets. (c) Methlyated DNA regions can also be target sites for nucleosome remodeling complexes.
- Figure 17-9a Three mechanisms that might be used to alter nucleosome structure by the ATP hydrolysis-dependent remodeling complex SWI/SNF. (a) DNA–histone contacts may be loosened. (b) The path of the DNA around an unaltered nucleosome core particle may be altered. (c) The conformation of the nucleosome core particle may be altered.
- Figure 17-9b Three mechanisms that might be used to alter nucleosome structure by the ATP hydrolysis-dependent remodeling complex SWI/SNF. (a) DNA–histone contacts may be loosened. (b) The path of the DNA around an unaltered nucleosome core particle may be altered. (c) The conformation of the nucleosome core particle may be altered.
- Figure 17-9c Three mechanisms that might be used to alter nucleosome structure by the ATP hydrolysis-dependent remodeling complex SWI/SNF. (a) DNA–histone contacts may be loosened. (b) The path of the DNA around an unaltered nucleosome core particle may be altered. (c) The conformation of the nucleosome core particle may be altered.
- Figure 17-10 Proposed model of the action of HAT and HD complexes. Transcription factors recruit the complex to the gene, which either adds or removes acetyl groups, aiding in either opening or closing the chromatin structure.
- Figure 17-11 The assembly of transcription factors required for the initiation of transcription by RNA polymerase II.
- Figure 17-13 Formation of DNA loops allows factors that bind to enhancers at a distance from the promoter to interact with regulatory proteins in the transcription complex and to maximize transcription.
- Figure 17-14 A helix–turn–helix or homeodomain in which (a) three planes of the -helix of the protein are established, and (b) these domains bind in the grooves of the DNA molecule.
- Figure 17-15 (a) A zinc finger in which cysteine and histidine residues bind to a atom. (b) This loops the amino acid chain out into a fingerlike configuration.
- Figure 17-16 (a) A leucine zipper is the result of dimers from leucine residue at every other turn of the -helix in facing stretches of two polypeptide chains. (b) When the -helical regions form a leucine zipper, the regions beyond the zipper form a Y-shaped region that grips the DNA in a scissorlike configuration.
- Figure 17-19a The restriction enzymes HpaII and MspI recognize and cut at CCGG sequences. (a) If the second cytosine is methylated (indicated by an asterisk), HpaII will not cut. (b) The enzyme MspI cuts at all CCGG sites, whether or not the second cytosine is methylated. Thus, the state of methylation of a given gene in a given tissue can be determined by cutting DNA extracted from that tissue with HpaII and MspI.
- Figure 17-19b The restriction enzymes HpaII and MspI recognize and cut at CCGG sequences. (a) If the second cytosine is methylated (indicated by an asterisk), HpaII will not cut. (b) The enzyme MspI cuts at all CCGG sites, whether or not the second cytosine is methylated. Thus, the state of methylation of a given gene in a given tissue can be determined by cutting DNA extracted from that tissue with HpaII and MspI.
- Figure 17-23 (Top) Organization of the Dscam gene in Drosophila melanogaster and the transcribed pre-mRNA. Each mRNA will contain one of the 12 possible exons for exon 4 (red), one of the 48 possible exons for exon 6 (blue), one of 33 for exon 9 (green), and one of 2 for exon 17 (yellow). If all possible combinations of these exons are used, the Dscam gene can encode 38,016 different versions of the DSCAM protein.
- Figure 17-23 (Top) Organization of the Dscam gene in Drosophila melanogaster and the transcribed pre-mRNA. Each mRNA will contain one of the 12 possible exons for exon 4 (red), one of the 48 possible exons for exon 6 (blue), one of 33 for exon 9 (green), and one of 2 for exon 17 (yellow). If all possible combinations of these exons are used, the Dscam gene can encode 38,016 different versions of the DSCAM protein.
- Figure 17-25 Mechanisms of gene regulation by RNA gene silencing. In the cytoplasm, two systems operate to silence genes. (Middle) In siRNA mediated silencing, a precursor RNA molecule is processed by Dicer, a protein with RNAse activity to form an antisense single stranded RNA that combines with a protein complex with endonuclease activity. siRNA/RISC (RNA-induced silencing complex) binds to mRNAs with complementary sequences, and cuts the mRNA into fragments that are degraded. This process is called RNAi in animal cells, and posttranslational gene silencing (PTGS) in plants. (Right) A partially double-stranded precursor is processed by Dicer to yield microRNA (miRNA) that binds to complementary -untranslated regions (UTRs) of mRNA, inhibiting translation. In plants, miRNAs cause arrest of translation. (Left) Small RNAs, processed by Dicer, play a role in RNA-directed DNA methylation (RdDM). These RNAs combine with DNA methyl transferases (DMTases) to methylate cytosine residues in promoter regions (purple circles), silencing genes.