Genomic Organization of H2Av Containing Nucleosomes in Drosophila Heterochromatin

Abstract

H2Av is a versatile histone variant that plays both positive and negative roles in transcription, DNA repair, and chromatin structure in Drosophila. H2Av, and its broader homolog H2A.Z, tend to be enriched toward 5′ ends of genes, and exist in both euchromatin and heterochromatin. Its organization around euchromatin genes and other features have been described in many eukaryotic model organisms. However, less is known about H2Av nucleosome organization in heterochromatin. Here we report the properties and organization of individual H2Av nucleosomes around genes and transposable elements located in Drosophila heterochromatic regions. We compare the similarity and differences with that found in euchromatic regions. Our analyses suggest that nucleosomes are intrinsically positioned on inverted repeats of DNA transposable elements such as those related to the “1360” element, but are not intrinsically positioned on retrotransposon-related elements.

ATP-Dependent Chromatin Remodeling Factors and Their Roles in Affecting Nucleosome Fiber Composition

“…Indeed, in vitro H2A.Z-containing nucleosome arrays were shown to be more tightly compacted than H2A-containing nucleosomes [ 133 ]. These observations are consistent with the results from genome-wide analyses of H2A.Z distribution that found that H2A.Z is present in heterochromatic areas of the genome [ 134 , 135 ].…”

Gene alterations at Drosophila inversion breakpoints provide prima facie evidence for natural selection as an explanation for rapid chromosomal evolution

“…In addition, only ~2.5 kb upstream of this gene is the ~90-kb block of Histone genes and TEs (see above). Because TEs may influence chromatin organization [ 86 ] and this in turn is a significant determinant of gene expression [ 87 , 88 ], the insertion of this block is likely to have altered the expression level and/or pattern of Dmoj\Hsp68b . No promoter or regulatory HSE sequences were detected upstream of Dmoj \ Hsp68a but according to D. mojavensis modENCODE DB this gene is being transcribed.…”

Histone Variants and Epigenetics

“…Indeed, this function may act globally, in parallel with the Set1 histone H3 methyltransferase, to prevent large-scale aberrant distribution of silencing factors (Venkatasubrahmanyam et al 2007). In metazoans, H2A.Z is also localized in facultative and constitutive heterochromatin, the inactive X chromosome, transposable elements, and pericentric heterochromatin (Greaves et al 2007;Draker and Cheung 2009;Boyarchuk et al 2011;Zhang and Pugh 2011).…”