RESUMO
We report the sequence, conservation and cell biology of a novel protein, Psc1, which is expressed and regulated within the embryonic pluripotent cell population of the mouse. The Psc1 sequence includes an RS domain and an RNA recognition motif (RRM), and a sequential arrangement of protein motifs that has not been demonstrated for other RS domain proteins. This arrangement was conserved in a second mouse protein (BAC34721). The identification of Psc1 and BAC34721 homologues in vertebrates and related proteins, more widely throughout evolution, defines a new family of RS domain proteins termed acidic rich RS (ARRS) domain proteins. Psc1 incorporated into the nuclear speckles, but demonstrated novel aspects of subcellular distribution including localization to speckles proximal to the nuclear periphery and localization to punctate structures in the cytoplasm termed cytospeckles. Integration of Psc1 into cytospeckles was dependent on the RRM. Cytospeckles were dynamic within the cytoplasm and appeared to traffic into the nucleus. These observations suggest a novel role in RNA metabolism for ARRS proteins.
Assuntos
Proteínas Nucleares/análise , Proteínas Nucleares/química , Proteínas/análise , Proteínas/química , Proteínas de Ligação a RNA/análise , Proteínas de Ligação a RNA/química , Transporte Ativo do Núcleo Celular , Sequência de Aminoácidos , Animais , Sítios de Ligação , Células COS , Núcleo Celular/química , Núcleo Celular/metabolismo , Estruturas do Núcleo Celular/química , Chlorocebus aethiops , Sequência Conservada , Citoplasma/química , Estruturas Citoplasmáticas/química , DNA Complementar/química , DNA Complementar/isolamento & purificação , Evolução Molecular , Camundongos , Microtúbulos/metabolismo , Dados de Sequência Molecular , Proteínas Nucleares/metabolismo , Estrutura Terciária de Proteína , Proteínas/metabolismo , Proteínas de Ligação a RNA/metabolismoRESUMO
Molecular and cellular analysis of early mammalian development is compromised by the experimental inaccessibility of the embryo. Pluripotent embryonic stem (ES) cells are derived from and retain many properties of the pluripotent founder population of the embryo, the inner cell mass. Experimental manipulation of these cells and their environment in vitro provides an opportunity for the development of differentiation systems which can be used for analysis of the molecular and cellular basis of embryogenesis. In this review we discuss strengths and weaknesses of the available ES cell differentiation methodologies and their relationship to events in vivo. Exploitation of these systems is providing novel insight into embryonic processes as diverse as cell lineage establishment, cell progression during differentiation, patterning, morphogenesis and the molecular basis for cell properties in the early mammalian embryo.
