IBYME   02675
INSTITUTO DE BIOLOGIA Y MEDICINA EXPERIMENTAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
In C2C12 cells Heterochromatin Protein 1γ interacts with actin to regulate gene expression and, in the cytoplasm, is associated to microfilaments
Autor/es:
PIWIEN-PILIPUK G.; GALIGNIANA N. M.,; CHARÓ N L,
Reunión:
Congreso; LXI Reunión científica anual. Sociedad Argentina de Investigación Clínica (SAIC); 2016
Resumen:
HP1 proteins belong to the chromodomain superfamily that in mammals correspond to HP1α,-β and -γ. HP1s, initially implicated in gene silencing, also participate in DNA repair, DNA replication, telomere stability and active transcription. We have previously shown that HP1γ, a protein so far exclusively nuclear, is also present in the cytoplasm of C2C12 myoblasts and myotubes. Importantly, myoblasts were unable to differentiate or gave rise to thin myotubes when the expression of HP1γ was interfered. Due to the filamentous pattern of staining of HP1γ observed in myoblasts, myotubes and myofibrils isolated from mice, we now explored its possible association with proteins of the cytoskeleton.In myoblasts, actin co-immunoprecipitates with HP1 in both nuclear and cytosolic fractions. Immunoelectron microscopic analysis performed in samples of murine skeletal muscle shows high-density immunogold particles that correspond to HP1γ localized to the Z-disk and the I- and A-bands of the sarcomere. These results raise the possibility that cytoplasmic HP1γ may play a role in sarcomere organization, which remains to be further explored. As for the role of the HP1γ-actin complex in the nucleus, a great body of evidence shows the importance of nuclear actin in the control of gene expression. Using chromatin immunoprecipitation (ChIP) assays, we show that both proteins are present in the promoter and transcribed region of the house keeping gene GAPDH. Further, re-ChIP analysis shows that both proteins belong in a complex associated to those same regions of GAPDH, suggesting that HP1γ may function as a scaffold protein for actin to bind to chromatin to regulate transcription. In summary, HP1γ forms complexes with actin in both the cytoplasm and the nucleus, which may regulate sarcomere organization in the cytoplasm and participate in the control of gene expression in the nuclear compartment.