SUMOylation promotes de novo targeting of HP1α to pericentric heterochromatin.

International audienceHP1 enrichment at pericentric heterochromatin is considered important for centromere function. Although HP1 binding to H3K9me3 can explain its accumulation at pericentric heterochromatin, how it is initially targeted there remains unclear. Here, in mouse cells, we reveal the presence of long nuclear noncoding transcripts corresponding to major satellite repeats at the periphery of pericentric heterochromatin. Furthermore, we find that major transcripts in the forward orientation specifically associate with SUMO-modified HP1 proteins. We identified this modification as SUMO-1 and mapped it in the hinge domain of HP1α. Notably, the hinge domain and its SUMOylation proved critical to promote the initial targeting of HP1α to pericentric domains using de novo localization assays, whereas they are dispensable for maintenance of HP1 domains. We propose that SUMO-HP1, through a specific association with major forward transcript, is guided at the pericentric heterochromatin domain to seed further HP1 localization

Xenopus HJURP and condensin II are required for CENP-A assembly

Chromatin structure imposed by condensin II at centromeres enables xHJURP-mediated incorporation of CENP-A

Modulation des propriétés intrinsèques et neurochimiques des motoneurones faciaux après axotomie

L axotomie du nerf facial est un bon modèle d étude de la plasticité neuronale dans le système nerveux périphérique. Durant les 2 premiers mois après lésion, l expression des ARNm codant les 3 sous-unités des canaux potassiques calcium-dépendant (SKi-3) et la sous-unité auxiliaire 31 des canaux sodiques voltage-dépendant est modifiée. La lésion modifie aussi sévèrement les propriétés neurochimiques des motoneurones. Les sous-unités majeures des récepteurs au GABA (GABAA CL1, 132 et y2 GABAB lb et 2) et au glutamate de type AMPA (GIuR2-4) sont fortement diminuées tant au niveau transcriptionnel que traductionnel. Ces résultats sont en accord avec l hypothèse selon laquelle, en réponse à une lésion, les motoneurones diminuent l expression des molécules dévolues à la transmission synaptique au profit de celles impliquées dans la régénération axonale. Le blocage d un facteur rétrograde périphérique, e silence neuronal, un signal lésionnel pourraient faire partie des signaux déclenchant.Facial nerve axotomy is a good model for studying neuronal plasticity in the peripheral nervous system. During the first 2 months after lesion, the expression pattern ol mRNA coding the 3 subunits of Ca2 activated K channel (SKi-3) and the f31 auxiliar subunit of the voltage-dependent sodium channels is modified. The lesion also severely modifies the neurochemical properties of the motoneurons. Major subunits of the GABI receptors (GABAA cLl, f32 and 2; GABAB lb and 2) and AMPA glutamate receptors (GIuR2-4) are strongly decreased as well at the level of mRNA and protein. These results are in agreement with the hypotheses according to which, in response to a lesion, the motoneurons decrease the expression of the molecules reserved for the synaptic transmission with the profit of those mplied in axonal regeneration. The blocking of a peripheral factor, the neuronal silence or an injury signal could be implied in these modulations.PARIS5-BU Saints-Pères (751062109) / SudocSudocFranceF