RELATIONSHIP BETWEEN A TRANSCRIPTION FACTOR, NF-Y AND ASH2L,A COMPONENT OF HISTONE METHYL TRANSFERASE, MLL COMPLEX.
Tesi di Dottorato
Data di Pubblicazione:
2011
Citazione:
RELATIONSHIP BETWEEN A TRANSCRIPTION FACTOR, NF-Y AND ASH2L,A COMPONENT OF HISTONE METHYL TRANSFERASE, MLL COMPLEX / A. Fossati ; tutor: Roberto Mantovani ; coordinatore: Roberto Mantovani. Universita' degli Studi di Milano, 2011 May 19. 23. ciclo, Anno Accademico 2010. [10.13130/fossati-andrea_phd2011-05-19].
Abstract:
Background.
Different histone post-translational modifications (PTMs) are crucial in the
regulation of chromatin, including methylations of H3 at Lysine 4 by the MLL
complex. A relevant issue is how this is causally correlated to the binding of
specific transcription factors (TFs) in regulatory regions. NF-Y is a TF that
regulates 30% of mammalian promoters containing the widespread CCAAT
element. We and others established that the presence of H3K4me3 is dependent
upon the binding of NF-Y. Here, we investigate the mechanisms of H3K4me3
deposition by NF-Y.
Methods.
We employed Chromatin Immunoprecipitation in cells in which Ash2L and NF-Y
subunits were knocked down by RNAi, to monitor the presence of histones PTMs
and components of the MLL complex. We performed gene expression profiling of
Ash2L-knocked down cells and analyzed the regulated genes. We performed
ChIPs in leukemic cells in which MLL1 is devoid of the methyltransferase
domain and fused to the AF4 gene.
Results.
Knock down of the Ash2L subunit of MLL leads to a decrease in global
H3K4me3 with a concomitant increase in H3K79me2. Knock down of NF-Y
subunits prevents promoter association of Ash2L, but not MLL1, nor WDR5, and
H3K4me3 drops dramatically. Endogenous NF-Y and Ash2L specifically interact
in vivo. Analysis of the promoters of Ash2L regulated genes, identified by
transcriptional profiling, suggests that a handful TF binding sites are moderately
enriched, among which the CCAAT box. Finally, leukemic cells carrying the
MLL-AF4 translocation show a decrease of H3K4me3, absence of Ash2L and
increase in H3K79me2, while NF-Y binding was not significantly affected.
Conclusions.
Three types of conclusions are reached: (i) H3K4 methylation is not absolutely
required for NF-Y promoter association. (ii) NF-Y acts upstream of H3K4me3
deposition by recruiting Ash2L. (iii) There is a general cross-talk between
H3K4me3 and H3K79me2 which is independent from the presence of MLL
oncogenic fusions.
Tipologia IRIS:
Tesi di dottorato
Elenco autori:
A. Fossati
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