Nuclear actin and protein 4.1: Essential interactions during nuclear assembly in vitro
AUTOR(ES)
Krauss, Sharon Wald
FONTE
National Academy of Sciences
RESUMO
Structural protein 4.1, which has crucial interactions within the spectrin–actin lattice of the human red cell membrane skeleton, also is widely distributed at diverse intracellular sites in nucleated cells. We previously showed that 4.1 is essential for assembly of functional nuclei in vitro and that the capacity of 4.1 to bind actin is required. Here we report that 4.1 and actin colocalize in mammalian cell nuclei using fluorescence microscopy and, by higher-resolution detergent-extracted cell whole-mount electron microscopy, are associated on nuclear filaments. We also devised a cell-free assay using Xenopus egg extract containing fluorescent actin to follow actin during nuclear assembly. By directly imaging actin under nonperturbing conditions, the total nuclear actin population is retained and visualized in situ relative to intact chromatin. We detected actin initially when chromatin and nuclear pores began assembling. As nuclear lamina assembled, but preceding DNA synthesis, actin distributed in a reticulated pattern throughout the nucleus. Protein 4.1 epitopes also were detected when actin began to accumulate in nuclei, producing a diffuse coincident pattern. As nuclei matured, actin was detected both coincident with and also independent of 4.1 epitopes. To test whether acquisition of nuclear actin is required for nuclear assembly, the actin inhibitor latrunculin A was added to Xenopus egg extracts during nuclear assembly. Latrunculin A strongly perturbed nuclear assembly and produced distorted nuclear structures containing neither actin nor protein 4.1. Our results suggest that actin as well as 4.1 is necessary for nuclear assembly and that 4.1–actin interactions may be critical.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=196875Documentos Relacionados
- Protein 4.1: its association with the human erythrocyte membrane.
- Protein interactions during coronavirus assembly.
- Assembly of nuclear ribonucleoprotein particles during in vitro transcription.
- Expression of cytoskeletal protein 4.1 during avian erythroid cellular maturation.
- Phosphorylation of protein 4.1 on tyrosine-418 modulates its function in vitro.