Nonhistoneproteins area heterogeneousgroupHalf of proteins in chromatin are nonhistones.Large number of nonhistone proteins,200-2,000,000 molecules perdiploidgenome.Largevariety of functionsScaffold-backboneofchromosomeDNAreplications-e.g.,DNA polymerasesChromosome segregation -e.g.,motor proteins of kinetochoresTranscriptional regulation-largest group regulatestranscription during gene expression (5,000-10,000 proteins inmammals)Occur in different amounts in different tissues because ofvarietyoffunction13-11
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-11 Nonhistone Nonhistone proteins proteins are a heterogeneous group. are a heterogeneous group. Half of proteins in chromatin are Half of proteins in chromatin are nonhistones nonhistones. Large number of Large number of nonhistone nonhistone proteins, 200 proteins, 200 – 2,000,000 molecules per 2,000,000 molecules per diploid genome. diploid genome. Large variety of functions Large variety of functions Scaffold Scaffold – backbone of chromosome backbone of chromosome DNA replications DNA replications – e.g., DNA polymerases e.g., DNA polymerases Chromosome segregation Chromosome segregation – e.g., motor proteins of e.g., motor proteins of kinetochores kinetochores Transcriptional regulation Transcriptional regulation – largest group regulates largest group regulates transcription during gene expression (5,000 transcription during gene expression (5,000 – 10,000 proteins in 10,000 proteins in mammals) mammals) Occur in different amounts in different tissues because of Occur in different amounts in different tissues because of variety of function. variety of function
Nonhistone proteins have diverse functionsCENP-E stainingHuman chromosome treated with detergentFig.11.1,11.213-12
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-12 Nonhistone proteins have diverse functions CENP-E staining Human chromosome treated with detergent Fig. 11.1, 11.2
11.2 Chromosome structure and compactionThe nucleosome is thefundamental unit ofchromosomalpackaging.Chromatin fibers withbeads havingdiameter of about 100A and strings havingdiameterof20AElectron microscopic pictures of nucleosomes(chicken cells)Fig.11.313-13
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-13 The nucleosome nucleosome is the fundamental unit of fundamental unit of chromosomal chromosomal packaging. packaging. Chromatin fibers with Chromatin fibers with beads having beads having diameter of about 100 diameter of about 100 Å and strings having and strings having diameter of 20 diameter of 20 Å. Fig. 11.3 Electron microscopic pictures of nucleosomes (chicken cells) 11.2 Chromosome structure and compaction 11.2 Chromosome structure and compaction
X-ray diffractionanalysisDNA does not coilsmoothly.Base sequencesdictatepreferrednucleosomepositionsalongDNA(b)H2EH3LinkerDNALinkerDNAX ray crystallography of nucleosome structureH113-14Fig. 11.4
Fig. 11.4 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-14 X ray crystallography of nucleosome structure X-ray diffraction ray diffraction analysis analysis DNA does not coil DNA does not coil smoothly. smoothly. Base sequences dictate Base sequences dictate preferred preferred nucleosome nucleosome positions along DNA. positions along DNA
(b)H2BH4H2AH3LinkerDNALinkerDNAH1Beadis a nucleosome with about 160 bp of DNA wrapped twice aroundacoreof8histones.40 bp of DNA link together nucleosomes.Fig.11.413-15
Fig. 11.4 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 13-15 Bead is a Bead is a nucleosome nucleosome with about with about 160 bp of DNA wrapped twice around wrapped twice around a core of 8 a core of 8 histones histones. 40 bp of DNA link together link together nucleosomes nucleosomes