Matrin 3: chromosomal distribution and protein interactions

Matrin 3 (matr3), an abundant protein of the internal nuclear matrix, has been linked to a variety of functional events. As a step toward defining its multifunctional nature, we have studied the association of matr3 with chromosome territories and identified potential interacting proteins. A similar staining pattern of matr3 was observed in fixed WI38 fibroblast cells and in live HeLa cells using a matr3-GFP construct. Matr3 was detected throughout autosomal and the active X chromosome territories. Conversely, matr3 was strikingly excluded from the inactive X chromosome as well as within both the perinuclear and perinucleolar heterochromatin. Yeast two hybrid analysis identified matr3 interactions with 33 unique nuclear localized proteins and also revealed its propensity for self association. A majority of these proteins are involved in RNA metabolism and chromatin remodeling while others function in protein translation, DNA replication/repair and apoptosis. Further analysis of a selection of these proteins and scaffold attachment factor A (SAFA) by co-localization and co-immunoprecipitation experiments using HeLa cells confirmed their interactions with matr3.