Organización de la estructura del ADN en cromosomas: bacterianos y eucariotas, Apuntes de Genética

¡Descarga Organización de la estructura del ADN en cromosomas: bacterianos y eucariotas y más Apuntes en PDF de Genética solo en Docsity! DE SANTIAGO DE COMPOSTELA Tema 4 Organización do ADN nos cromosomas  Bacteria lisada Lonxitude ADN E. coli ~1000 x lonxitude da celula Superenrolamento JAP A Sy A > Relaxed < S circular DNA Ss $ : S A (b) Add two turns (c) Remove two turns (overrotate) (underrotate) AA ——, supercoil supercoil Figure 11-2 Genetics: A Conceptual Approach, Third Edition 0 2009 W.H. Freeman and Company  Empaquetamento: estructura terciaria Superenrolamento B – ADN relaxado: 10 pb por volta Superenrolamento Sen cabos ceibes: - ADN circular - ADN “pinzado” con proteínas E. coll Bind strand 1 red) Pass strand II blue) through e pd Ciose strand Release DNA DNA is e E. http://www.bio.davidson.edu/courses/genomics/2003/baxter/mfyg.html UNREGISTERED :) downloadhelper et  Cromosoma bacteriano Circular http://textbookofbacteriology.net/haemophilus.html A map of the circular chromosome of Haemophilus influenzae illustrating the location of known genes and predicted coding regions. Cromosoma bacteriano Not all bacteria have a single circular chromosome: some bacteria have multiple circular chromosomes, and many bacteria, like Streptomyces, have linear chromosomes and linear plasmids.) http://www.nature.com/nature/journal/v417/n6885/full/417141a.html Cromosoma bacteriano Circular Estabilizado e compactado por interacción con complexos de moitas proteínas (Not all bacteria have a single circular chromosome: some bacteria have multiple circular chromosomes, and many bacteria, like Streptomyces, have linear chromosomes and linear plasmids.) http://www.sci.sdsu.edu/~smaloy/MicrobialGenetics/topics/chroms-genes-prots/chromosomes.html Cromosoma bacteriano Rachando a bacteria, o ADN espállase en rolos Cromosoma eucariota O grao de condensación do ADN varía: Interfase: moi condensado Mitose: extremadamente condensado ~ 1,8 m ! Cromosoma eucariota O grao de condensación do ADN varía: Interfase: moi condensado Mitose: extremadamente condensado http://www.shmoop.com/dna/dna-packaging.html Cromosoma eucariota Complexo ADN – proteínas: CROMATINA Cambios de grao de condensación A meirande parte da cromatina Transcripción Eucromatina Heterocromatina Decote moi condensada Centrómeros, telómeros, Cromosoma X inactivado Meirande parte Chr Y Outras seccións Cromosoma eucariota 10 o Ar 1Ala rn A a ME! laa Nucleolo  Cromosoma eucariota Complexo ADN – proteínas: CROMATINA Eucromatina Heterocromatina Centrómeros, telómeros, Meirande parte Chr Y Cromosoma X inactivado Constitutiva Facultativa Cromosoma eucariotaCROMATINA principal componhente: HISTONAS Ricas en Arxinina e Lisina: carga positiva Atracción cargas negativas ADN http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/Lys_arg.gif Cromosoma eucariota Elemento básico da cromatina: NUCLEOSOMA 2 x H2A, H2B, H3, H4 2 Voltas de ADN, 145 – 147 pb nucleosoma cromatosoma CROMATINA principal componhente: HISTONAS: 5 castes principais Table 11.1 Characteristics of histone proteins Histone Molecular Number of Protein Weight Amino Acids H1 21,130 223 H2A 13,960 129 H2B 13,774 125 H3 15,273 135 H4 11,236 102 Note: The sizes of H1, H2A, and H2B histones vary somewhat from species to species. The values given are for bovine histones. Source: Data are from A. L. Lehninger, D. L. Nelson, and M. M. Cox, Principles of Biochemistry, 3d ed. (New York: Worth Publishers, 1993), p. 924.  Elemento básico da cromatina: NUCLEOSOMA Cada histona no nucleosoma ten unha cola flexible de 11-37 aminoácidos que asoma fora do nucleosoma http://ec.asm.org/content/9/8/1138/F1.large.jpg K: Lisina R: Arxinina Elemento básico da cromatina: NUCLEOSOMA Os aminoacidos cargados positivamente nisa cola interactuan coas cargas negativas dos fosfatos do ADN K: Lisina R: Arxinina Elemento básico da cromatina: NUCLEOSOMA Tamen poden interactuar con nucleosomas próximos, o que axuda a compactar o ADN entre nucleosomas K: Lisina R: Arxinina Estructura cromatínica de orde superior http://a-chien.blogspot.com.es/2013_05_01_archive.html Estructura cromatínica de orde superior Cromatina condensada: Nucleosomas pregados sobre si mesmos . - Microfotografia - 4 Es Jo - electrónicade ' A E e) » » % DS ; nucleosomas” a, ¡05 5 A de Individual ar” 7 nudleosomes — 2 9 > so. Als ¡2 ld Figure 11-7a Genetics: A Conceptual Approach, Third Edition 9 2009 W.H. Freeman and Company  EJ Each nucleosome consists of eight histone proteins around which the DNA wraps 1.65 times. E double helix yA ID At the simplest level, <hromatin is a double- stranded helical structure of DNA. ye AY with histones to form nucleosomes. A chromatosome consists ofa nucleosome plus the H1 histone. Histone H1 «««Ehat forms loops averaging 300 nm in length. Nucleosome core of eight histone molecules e Lo EA The 300-nm fibers are compressed and folded to produce a 250-nm-wide fiber. 300 nm su NOS y 3 fiber produces the chromatid 250-nm-wide fiber of a chromosome. AIN ANA 700 nm EJ The nucleosomes fold up to produce a 30-nm fiber... Características Y variabeis... Figure 11-5 Genetics: A Conceptual Approach, Third Edition Water Glucose Antibody Virus Bacteria Cancer cell % 2009 W.H.Freeman and Company A period Tennis ball Short region of DNA double helix Características variabeis... "Beads ona string” ==, torm of chromatin 30-nm chromatin tibre of packed nucleosomes Section of chromosome in an extended form Water — Glucose Antibody Virus Bacteria Cancercell A period Tennis ball Condensed section y P > of chromosome 58 E F L a Entire mitotic chromosome  2nm 300 nm Chromaline DNA loops bn" Condensed chromatine  C am b | OS Question: Is chromatin structure altered during transcription? DNAs sensitivity to DNase | was tested on different n a tissues and at different times in development. Key . Embryonic Adult DNA highly globingene globin genes sensitive estructura cuca praia sensitive, d a U a añ , CO Erythroblasts o cromatina first 24 hours U 0 | YA Erythroblasts En 5 days -. - al | al Erythroblasts 14 days O Brain cells throughout — 0 — 0 Expresado development U ab qgA  Question: Is chromatin structure altered during transcription? DNAss sensitivity to DNase | was tested on different tissues and at different times in development. Chicken DNA CO Erythroblasts first 24 hours Erythroblasts 5 days Erythroblasts 14 days Brain cells throughout development Conclusion: Sensitivity of DNA to digestion by DNase l is correlated with gene expression, suggesting that chromatin structure changes during transcription. Embryonic Adult globingene globin genes [ma] Em U a ar mu SER E EE uu Ea U a añ Ea E EN Ea U a a = = U a. añ En E mu E Ea U a. añ Key [DNA highly sensitive to DNasel Before hemoglobin synthesis, none of the globin genes are sensitive to DNase | digestion. After globin synthesis has begun, all genes are sensitive to DNase l, but the embryonic globin gene U is the most sensitive. In the 14-day-old embryo, when only adult hemoglobin is expressed, adult genes are most sensitive and the embryonic gene is insensitive. Globin genes in the brain— which does not produce globin—remain insensitive throughout development. as Figure 11-9 Genetics: A Conceptual Approach, Third Edition 9 2009 W.H. Freeman and Company  Relaxación asociada ca transcripción Exemplo: ACETILACION Histone acetyltransferases (HATs) and histone deacetylases (HDACs) http://sphweb.bumc.bu.edu/otlt/MPH-Modules/PH/PH709_DNA-Genetics/PH709_DNA-Genetics29.html Acetyl group ACETILACION a Closed chromatin: transcriptional repression b Open chromatin: transcriptional activation HDAG HDAG Nature Reviews | Drug Discovery  ACETILACION Nucleosomes consist of DNA (black line) wrapped around histone octomers (purple). Post-translational modification of histone tails by methylation (Me), phosphorylation (P) or acetylation (Ac) can alter the higher-order nucleosome structure. Nucleosome structure can be regulated by ATP-dependent chromatin remodellers (yellow cylinders), and the opposing actions of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Methyl-binding proteins, such as the methyl-CpG-binding protein (MECP2), target methylated DNA (yellow) and recruit HDACs. a | DNA methylation and histone deacetylation induce a closed-chromatin configuration and transcriptional repression. b | Histone acetylation and demethylation of DNA relaxes chromatin, and allows transcriptional activation. http://www.nature.com/nrd/journal/v1/n4/fig_tab/nrd772_F1.html METILACION de HISTONAS Methyl groups are transferred to amino acids of histone proteins that make up nucleosomes. This can either increase or decrease transcription of genes, depending on which amino acids in the histones are methylated, and how many methyl groups are attached. https://en.wikipedia.org/wiki/Histone_methylation http://pharmacy.wisc.edu/jiang-lab/research Estructura do cromosoma eucariota Telomeros Telomeros Brazo curto (p) Brazo longo (q) Rexión do centrómero Estructura do cromosoma silver nitrate reacts preferentially with regions of constitutive heterochromatin: • Centromeres • Telomeres http://www.sciencedirect.com/science/article/pii/S0091679X08004238 Ihttp://link.springer.com/article/10.1007%2FBF00983553#page-1 Centrómero Estructura do cromosoma Scanning electron micrographs of barley metaphase chromosomes stained with silver compounds showing general protein distribution. BSE (Back-Scattered Electrons) images show that silver nitrate reacts preferentially with chromatin in the centromeres and telomeres http://www.sciencedirect.com/science/article/pii/S0091679X08004238 http://www.mcatzone.com/uploads/gloss/chromatid.jpg Cinetocoros Estructuras proteicas ensambladas no centrómero que xunguen o cromosoma as fibras do huso Electron micrograph of kinetochore – place of microtubules attachment on a chromosome. Metaphase of a human lung cell in tissue culture. Note the insertion of microtubules in the centromeres (arrows) of the densely stained chromosomes. Reduced from x50,000. http://intranet.tdmu.edu.ua/data/kafedra/ internal/histolog/classes_stud/English/m edical/II%20term/03%20Cytology %20Cells%20reproduction%20Aging %20and%20death%20of%20the %20cell.htm http://sun.menloschool.org/~dspence/b iology/mit_meiosis/images/centromere 2.jpg Cinetocoros Centrómero * Control da mitose (Regulación...) * Sinal procedente do centrómero: deten a anafase * Desaparece cando TODOLOS cromosomas se xunguiron o huso * Encétase a anafase Centrómero * Secuencia: centos de miles de pb * Secuencias curtas repetidas milleiros de veces * Illas mais complexas… Sacharomyces: Secuencia de 3 rexións que se repite moitas veces no centrómero: non codifica proteínas Centrómero ... • Summary of physical differences between CENP-A- and H3-containing nucleosomal arrays. • CENP-A-containing arrays are generally more condensed than canonical arrays upon folding (indicated by closer spacing of adjacent CENP-A- containing nucleosomes). http://www.pnas.org/content/108/40/16588/F5.expansion.html ¡Ol Eg] nucleolares  Nucleolar organizer regions (NORs) are chromosomal landmarks ... that consist of tandemly repeated sequences of ribosomal genes (rRNA). Organizadores nucleolares http://www.nature.com/hdy/journal/v108/n1/full/hdy2011105a.html http://web.udl.es/usuaris/e4650869/docencia/practiques_on-line/cariotips/nous_cariotips/metodes/nor-staining.html • Acrocentric chromosomes: • They have submetacentric centromere with short arm and long arm, and satellite material in the NOR. • They are human chromosomes 13, 14, 15, 21, 22 Organizadores nucleolares Centromere http://aangelpathology.com/index.php/ap-cp-notes/item/660-conventional-cytogenetics-and-cancer The satellite at metaphase appears to be attached to the rest of the body of chromosomes by a thread of chromatin. https://en.wikipedia.org/wiki/Satellite_chromosome ¡Ol Eg] nucleolares 50 mil Coxsackie and adenovirus receptor O Myeloproliferative syndr Amyloidosis, cerebroarterial, Dutch type Alzheimer disease, APP-related Schizophrenia, chronic | Usher syndrome, autosomal recessive Amytrophic lateral sclerosis | Oligomycin sensitivity Jervell and Lange-Nielsen syndrome i Long QT syndrome y Dovvn syndrome cell adhesion molecule Epilepsy, progressive myoclonic Homocystinuria Holoprosencephaly, alobar ateract, congenital, autosomal dominant Knobloch syndrome Deafness, autosomal recessive Hemolytic anemia Myxovirus (influenza) resistance Breast cancer Leukemia, acute myeloid Platelet disorder, with myeloid malignancy htip://upload wikimedia.org/wikipedia/en/d/d6/Human_chromosome_21.png  Organizadores nucleolares The nucleolus is a ribosome production factory Actively growing mammalian cells... contain 5 million to 10 million ribosomes. http://www.sivabio.50webs.com/nucleus.htm http://www.google.es/imgres? imgurl=http://i.ytimg.com/vi/Uwj3Lu6Qne0/hqdefault.jpg&imgrefurl=http://www.yout ube.com/watch?v%3DUwj3Lu6Qne0&h=360&w=480&tbnid=s- M2x429a7ViLM:&docid=fFmPmU8RWOjlOM&ei=0ckKVqj3FojZU8mqoIgP&tbm=is ch&client=ubuntu&ved=0CDMQMygTMBNqFQoTCOij_O_hnMgCFYjsFAodSRUI8 Q Luis Cromosomas fracturados: Extremos inestabeis => Adhesións Degradación Luis Cromosomas integros: Extremos protexidos mu»  Secuencias repetitivas características (250 – 1500 veces) Telómeros * Secuencia humana 5’ CCCTAA… 3’ GGGATT… * Telómeros + A cadea rica en G adoita asomaren no extremo: + POT (Protection of Telomeres Proteins) http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Protein_POT1_PDB_1xjv.png/220px-Protein_POT1_PDB_1xjv.png A protectora dos telómeros POT1 (azul intenso) unese a secuencia específica TTAGGG que se repite no ADN que asoma nos telómeros Esta a sua vez unese a proteína TTP1 (branco y azul claro) que aumenta a afinidade de POT1 po la freba de ADN. http://flagellum.wordpress.com/category/genetica/page/3/ O Figure 11-12b Genetics: A Conceptual Approach, Third Edition 0 2009 W.H. Freeman and Company G-rich single- stranded overhang vá ollo Y eee: cy  En mamíferos: Bucle en t Parallel-stranded DNA can exist under normal solution conditions, but competition experiments show it to be thermodynamically less favorable than the conventional antiparallel form. http://www.ncbi.nlm.nih.gov/pubmed/2468357 En mamíferos: Bucle en t T-loop. The ends of mammalian chromosomes end in giant duplex loops, called t-loops. In this photo, telomeric DNA from cultured human tissue cells is shown arranged in a t-loop conformation. http://www.nature.com/scitable/topicpage/telomeres-of-human-chromosomes-21041 Cromosomas eucariotas artificiais