Investigations of the pathway of incorporation and function of lamin A in the nuclear lamina

✍ Scribed by Dyer, Joanna A.; Lane, Birgitte E.; Hutchison, Christopher J.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 234 KB
• Volume: 45
• Category: Article
• ISSN: 1059-910X
• DOI: 10.1002/(sici)1097-0029(19990401)45:1<1::aid-jemt1>3.0.co;2-z

✦ Synopsis

Cell-free extracts of Xenopus eggs were used to investigate how differing lamin sub-types are incorporated into a lamina and how lamina composition influences DNA replication. Purified recombinant human lamin A (HlaminA) was inoculated into egg extracts, which support in vitro nuclear assembly. The route of incorporation of Hlamin A into the lamina was compared to Xenopus lamin B 3 (XlaminB 3 ), the major endogenous lamin sub-type in egg extracts. While Xlamin B 3 was incorporated into the lamina directly, HlaminA first accumulated at nucleoplasmic foci, before entering the lamina. When HlaminA was inoculated into extracts depleted of XlaminB 3 it entered nuclei efficiently and was incorporated into nucleoplasmic foci. However, in the absence of XlaminB 3 , HlaminA remained in the foci and did not enter the nuclear envelope. When HlaminA entered the nuclear envelope, it did not influence DNA replication. Nuclei containing HlaminA initiated DNA replication on queue and in addition the spatial distribution of replication centres in these nuclei was identical to controls. Taken together, these results suggest that the incorporation of A-type lamins into the nuclear envelope is dependent upon the presence of B-type lamins. However, the presence of A-type lamins alone is not sufficient to influence the spatial and temporal order of DNA replication.