Dissecting relative contributions of cis- and trans-determinants to nucleosome distribution by comparing Tetrahymena macronuclear and micronuclear chromatin
نویسندگان
چکیده
The ciliate protozoan Tetrahymena thermophila contains two types of structurally and functionally differentiated nuclei: the transcriptionally active somatic macronucleus (MAC) and the transcriptionally silent germ-line micronucleus (MIC). Here, we demonstrate that MAC features well-positioned nucleosomes downstream of transcription start sites and flanking splice sites. Transcription-associated trans-determinants promote nucleosome positioning in MAC. By contrast, nucleosomes in MIC are dramatically delocalized. Nucleosome occupancy in MAC and MIC are nonetheless highly correlated with each other, as well as with in vitro reconstitution and predictions based upon DNA sequence features, revealing unexpectedly strong contributions from cis-determinants. In particular, well-positioned nucleosomes are often matched with GC content oscillations. As many nucleosomes are coordinately accommodated by both cis- and trans-determinants, we propose that their distribution is shaped by the impact of these nucleosomes on the mutational and transcriptional landscape, and driven by evolutionary selection.
منابع مشابه
Dissecting cis and trans Determinants of Nucleosome Positioning: A Dissertation
Eukaryotic DNA is packaged in chromatin, whose repeating subunit, the nucleosome, consists of an octamer of histone proteins wrapped by about 147bp of DNA. This packaging affects the accessibility of DNA and hence any process that occurs on DNA, such as replication, repair, and transcription. An early observation from genome-wide nucleosome mapping in yeast was that genes had a surprisingly cha...
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