IBYME   02675
INSTITUTO DE BIOLOGIA Y MEDICINA EXPERIMENTAL
Unidad Ejecutora - UE
artículos
Título:
Heterochromatin Protein 1γ is in the nucleus but also in the cytoplasm interacting with actin in both cell compartments
Autor/es:
N. M. GALIGNIANA; G. PIWIEN PILIPUK; N. CHARO
Revista:
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2017 vol. 1865 p. 432 - 443
ISSN:
0167-4889
Resumen:
Confocal and electron microscopy images, and WB analysis of cellular fractions revealed that HP1g is in the nucleus but also in the cytoplasm of C2C12 myoblasts, myotubes, skeletal and cardiac muscles, N2a, HeLa and HEK293T cells. Signal specificity was tested with different antibodies and by HP1g knockdown. Leptomycin B treatment of myoblasts increased nuclear HP1g, suggesting that its nuclear export is Crm-1-dependent. HP1g exhibited a filamentous pattern of staining partially co-localizing with actin in the cytoplasm of myotubes and myofibrils. Immunoelectron microscopic analysis showed high-density immunogold particles that correspond to HP1g localized to the Z-disk and A-band of the sarcomere of skeletal muscle. HP1g partially co-localized with actin in C2C12 myotubes and murine myofibrils. Importantly, actin co-immunoprecipitated with HP1g in the nuclear and cytosolic fractions of myoblasts. Actin co-immunoprecipitated with HP1g in myoblasts incubated in the absence or presence of the actin depolimerizing agent cytochalasin D, suggesting that HP1g may interact with G-and F-actin. In the cytoplasm, HP1g was associated to the perinuclear actin cap that controls nuclear shape and position. In the nucleus, re-ChIP assays showed that HP1g-actin associates to the promoter and transcribed regions of the house keeping gene GAPDH, suggesting that HP1γ may function as a scaffold protein for the recruitment of actin to control gene expression. When HP1g was knocked-down, myoblasts were unable to differentiate or originated thin myotubes. In summary, HP1g is present in the nucleus and the cytoplasm interacting with actin, a protein complex that may exert different functions depending on its subcellular localization.