MSA-35: a protein identified by human autoantibodies that colocalizes with microtubules.

We have identified a putative 35-kilodalton protein that colocalizes with microtubules and displays a unique spatial and temporal distribution during the cell cycle of HeLa cells. This protein has been given the designation MSA-35. MSA-35 first appears in association with microtubules and centrosomes of interphase cells exhibiting centrosome separation as a prelude to cell division. This protein is found in conjunction with kinetochore microtubules throughout their appearance. MSA-35 transiently associates with interpolar microtubules following anaphase and the pattern of MSA-35 reactivity in telophase cells suggests that there are at least seven domains within the intercellular bridge. The distribution of MSA-35 during and following recovery from mitotic arrest with nocodazole suggest that it is also present at low levels in interphase cells, can associate with interphase centrosomes, and colocalizes with nascent microtubules. The complex spatial and temporal distribution of MSA-35 indicates that it may be necessary for a series of events in the mitotic process such as the bundling of microtubules.     

A histone 1-like antigen is a component of the nuclear envelope

Rabbit antibodies have been raised against rat liver nuclear envelopes. An enzyme-linked immunosorbent assay (ELISA) demonstrated high titer antiserum specific for the nuclear envelope preparation. Immunocytochemical studies showed that the antiserum stained the nuclear envelopes, but not intra-nuclear components of HEp-2 (human malignant epithelial) cells. When electrophoretically separated peptides were tested by immunoblotting techniques, the rabbit antiserum specifically stained proteins with molecular masses of 26 and 28 kD. These peptides had similar mobilities to purified histone 1 (H1). Indeed purified calf thymus H1 recognized the antiserum. The antigens are not loosely bound to the nuclear envelope, as they could not be extracted with low salt. Therefore, we have established that the 26 and 28 kD nuclear envelope peptides are not contaminants of the nuclear envelope preparation and that they express determinants that are immunologically cross-reactive with purified H1, but not with intra-nuclear H1.     

Detection of distinct structural domains within the primary constriction using autoantibodies

We report the immunological differentiation of structures within the primary constriction. These include the kinetochore and the connecting strand, a structure which connects sister kinetochores. The location and temporal appearance of the connecting strand antigen suggest that it could play a role in the maintenance of sister chromatid pairing. In addition, we report the identification of a novel epitope that is localized to discrete patches along the entire length of the junction between sister chromatids at metaphase (the junction patch antigen). The patches on the inner surface of the euchromatic arms can be disrupted by Colcemid treatment while those found in the primary constriction remain intact. The apparent heterogeneity of the patches suggests that they may play different roles in the regulation of sister chromatid pairing. Because of their cytological localization and possible functional role, the junction patch and connecting strand antigens have provisionally been collectively termed CLiPs (Chromatid Linking Proteins'). All of these antigenic sites are shown to be distinct from centromeric heterochromatin, which can itself be immunologically differentiated from the euchromatic arms. The relationship between the antigenicity of the primary constriction and the unique manner in which chromatin is organized in this region is discussed.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.