Two new chromodomain-containing proteins that associate with heterochromatin in <Emphasis Type="Italic">Sciara coprophila</Emphasis> chromosomes |
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Authors: | Patricia G Greciano Maria Fernanda Ruiz Leonor Kremer Clara Goday |
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Institution: | (1) Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain;(2) Protein Tools Unit, Centro Nacional de Biotecnología, CSIC, 28049 Madrid, Spain |
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Abstract: | We report here the molecular and cytological characterization of two proteins, ScoHET1 and ScoHET2 (for Sciara coprophila heterochromatin), which associate to constitutive heterochromatin in the dipteran S. coprophila. Both proteins, ScoHET1 of 37 kDa and ScoHET2 of 44 kDa, display two chromodomain motifs that contain the conserved residues
essential for the recognition of methylated histone H3 at lysine 9. We raised antibodies to analyze the chromosomal location
of ScoHET1 and ScoHET2 in somatic and germline cells. In S. coprophila polytene chromosomes, both proteins associate to the pericentromeric regions and to the heterochromatic subterminal bands
of the chromosomes. In germinal nuclei, ScoHET1 and ScoHET2 proteins distribute to the heterochromatic regions of the regular
chromosome complement and are abundantly present along the heterochromatic germline-limited “L” chromosomes. We investigated
histone methylation modifications and found that all heterochromatic regions enriched in ScoHET1/ScoHET2 proteins exhibit
high levels of di- and tri-methylated histone H3 at lysine 9. Taken together, our results support that the association of
ScoHET1/ScoHET2 to heterochromatin is mediated by histone H3K9 methylation. Using 5-methylcytosine antibodies, we proved the
cytological detection of DNA methylation in S. coprophila. From our observations in L germline chromosomes, heterochromatin in S. coprophila is highly enriched in DNA 5-methylcytosine residues.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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