Shortest nucleosomal repeat lengths during sea urchin development are found in two-cell embryos.

Published

Journal Article

Prior to fertilization, sperm possess one of the longest nucleosome repeat lengths yet determined [approximately 250 base pairs (bp) for the sea urchin Strongylocentrotus purpuratus]. We show here that the two-cell embryo has an average repeat size of 189 +/- 2 bp as probed by micrococcal nuclease; this is the shortest average nucleosomal subunit reported for S. purpuratus. By the eight-cell stage, the average nucleosome repeat increases to 201 +/- 2 bp, and it subsequently increases further during development. These results indicate that a dramatic rearrangement of chromatin occurs upon fertilization and that this chromatin remodeling continues through early development. When two-cell embryos are labeled for 30 min with [3H]thymidine and digested briefly, they exhibit nuclease-hypersensitive fragments averaging 308 bp in size, which are consistent with the size of protected DNA units in replication intermediate complexes at blastula stage (as described by Levy and Jacob [Levy, A., & Jacob, K. M. (1978) Cell (Cambridge, Mass.) 14, 259]). Our results are consistent with two general propositions: (1) long repeat lengths are found in highly differentiated cells, and (2) short repeat lengths are characteristic of cells more active in cell division. Our data would also imply that a rapid increase in the DNA complement, e.g., in the transition from haploid to diploid state following fertilization, is accompanied by a shortening of the average size of DNA in a nucleosome after replication.

Full Text

Duke Authors

Cited Authors

  • Chambers, SA; Vaughn, JP; Shaw, BR

Published Date

  • November 1, 1983

Published In

Volume / Issue

  • 22 / 24

Start / End Page

  • 5626 - 5631

PubMed ID

  • 6686059

Pubmed Central ID

  • 6686059

Electronic International Standard Serial Number (EISSN)

  • 1520-4995

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi00293a026

Language

  • eng