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Accueil du site > Animations Scientifiques > Séminaires 2008 > Chromatin remodeling during early development : which role for HIRA in Drosophila ?

Chromatin remodeling during early development : which role for HIRA in Drosophila ?

Orateur :

Pierre Couble, Assemblage de la Chromatine et Développement, Centre de Génétique Moléculaire et Cellulaire, Lyon

Salle :

C023 (RDC LR6 côté CECAM)

Sujet :

Upon fertilization, chromatin undergoes profound remodeling. Indeed, an important step of zygote formation in sexually reproducing animals is the decondensation of the fertilizing sperm nucleus into a replication-competent male pronucleus. Sperm specific chromosomal proteins, including protamines, are replaced with maternally-provided histones to form the male pronucleus. By studying a mutant allele of the Drosophila Hira gene, we showed that the chaperone HIRA is essential for the assembly of paternal chromatin at fertilization. During this replication-independent process, HIRA deposits nucleosomes containing the histone variant H3.3 on paternal DNA, in a genome-wide manner. Sperm chromatin remodeling is thus under the control of a specific nucleosome assembly machinery. To further dissect the functions of HIRA during development, a loss-of-function allele of Hira was generated. If, as expected, the absence of maternal HIRA impairs sperm decondensation, homozygous flies with the null allele are viable. This strongly suggests that besides sperm chromatin remodeling other functions of HIRA are dispensable in Drosophila. This surprising observation is discussed in the light of a growing body of data on the role of HIRA in animals.

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