ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The chromatin fraction of transcriptionally active macronuclei ofStylonychia lemnae shows a typical core histone pattern after SDS-polyacrylamide gel electrophoresis (SDS-PAGE). However, extracts of transcriptionally inactive micronuclei display only two bands in the molecular weight range of macronuclear core histones, corresponding to macronuclear H2A/H2B and H4. While a band corresponding to macronuclear H3 cannot be detected, the micronuclear fraction contains a prominent Mr 21,000 protein (protein X). We examined the chromatin fractions of the two kinds of nuclei in detail using specific antibodies directed against core histones and synthetic peptides of histones. Both microand macronuclei contain histones that are specifically recognized by antibodies directed against H2A, H2B and H4. Antigenicity in association with core histone H3 is found only in the macronuclear anlagen and in macronuclear extracts. None of the antibodies used react with the micronucleus specific protein X. During macronuclear development protein X disappears while macronuclear H3 appears. Thus we speculate, that protein X may be functionally related to macronuclear H3. The inactive state of the micronucleus is also characterized by the presence of two proteins, Y1 and Y2, with apparent Mrs of 45,000 in SDS-polyacrylamide gels. These proteins are recognized by antibodies raised against the N-terminal peptide of H3 and the C-terminal peptide of H2B respectively. Y1 and Y2 are also present during all of the transcriptionally inactive stages of macronuclear development but are not found in the active macronucleus. By these means chromatin extracts of micronuclei, macronuclear anlagen and macronuclei can be clearly distinguished. The observed differences reveal a sequence of changes in chromatin organization that correlate with the transition from the transcriptionally inactive to the transcriptionally active state of the chromatin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01726691
