Something newaPre-mRNA(Py)10-20xcagGAGguPuaguNucleosomebDNAPolIIPre-mRNATilgner, H.et al.Nucleosome positioning as a determinant of exon recognitionNature Struct. Mol. Biol. 16, 996-1001 (2009)Schwartz, S.et al.Chromatin organization marks exon-intron structure.NatureStruct. Mol. Biol. 16, 990-995 (2009)Andersson, R. et al. Nucleosomes are well positioned in exons and carrycharacteristichistonemodifications.GenomeRes.19,1732-41(2009)When chromatin meets splicing. Nature Struct. Mol. Biol. 16, 902 - 903 (2009)Chromatin:Apeakforexons.NatureRev.Genet.10,664-665(October2009)
Something new • Tilgner, H. et al. Nucleosome positioning as a determinant of exon recognition. Nature Struct. Mol. Biol. 16, 996–1001 (2009) • Schwartz, S. et al. Chromatin organization marks exon–intron structure. Nature Struct. Mol. Biol. 16, 990–995 (2009) • Andersson, R. et al. Nucleosomes are well positioned in exons and carry characteristic histone modifications. Genome Res. 19, 1732-41 (2009). • When chromatin meets splicing. Nature Struct. Mol. Biol. 16, 902 - 903 (2009) • Chromatin: A peak for exons. Nature Rev. Genet. 10, 664-665 (October 2009)
Something New:The long-standing view of chromosome packaging is that10-nm beads-on-a string chromatin fibres fold intohigherorder 30-nm fibres, which further twist and coil toform highly condensed chromosomes. Nishino et al (2012) demonstrates that regular 30-nmfibres are absentfromhumanmitotic chromosomes.Theemerging view is that chromosome-level condensationcan be achieved through packaging of 10-nm fibres in afractal manner.1Hansen JC:Humanmitoticchromosomestructure:whathappenedtothe30-nmfibre?EMBOJ2012,31:1621-16232.Nishino Y,etal.:Human mitotic chromosomes consistpredominantly ofirregularlyfoldednucleosomefibreswithouta3-nmchromatinstructure.EMBOJ2012,31:1644-1653
Something New • The long-standing view of chromosome packaging is that 10-nm beads-on-a string chromatin fibres fold into higherorder 30-nm fibres, which further twist and coil to form highly condensed chromosomes. • Nishino et al (2012) demonstrates that regular 30-nm fibres are absent from human mitotic chromosomes. The emerging view is that chromosome-level condensation can be achieved through packaging of 10-nm fibres in a fractal manner. • 1. Hansen JC: Human mitotic chromosome structure: what happened to the 30- nm fibre? EMBO J 2012, 31:1621-1623. • 2. Nishino Y, et al.: Human mitotic chromosomes consist predominantly of irregularly folded nucleosome fibres without a 30-nm chromatin structure. EMBO J 2012, 31:1644-1653
The typical appearance of a metaphasechromosomeCentromereTelomereChromatid
The typical appearance of a metaphase chromosome
Untypical chromosomesMinichromosomes and macrochromosomesBchromosomesHolocentric chromosomes, in CaenorhabditiselegansHeterochromatin: nottotally silenced
Untypical chromosomes • Minichromosomes and macrochromosomes • B chromosomes • Holocentric chromosomes，in Caenorhabditis elegans • Heterochromatin: not totally silenced
: Arabidopsis centromeres span 0.9-1.2 Mb ofDNA and each one is made up largely of 180-bprepeat sequences. In humans the eguivalentsequences are 171 bp and are called alphoidDNA.The special centromeric proteins in humansinclude at least seven that are not foundelsewhere in the chromosome
• Arabidopsis centromeres span 0.9-1.2 Mb of DNA and each one is made up largely of 180-bp repeat sequences. In humans the equivalent sequences are 171 bp and are called alphoid DNA. • The special centromeric proteins in humans include at least seven that are not found elsewhere in the chromosome