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J J Maio

Publications and source records attributed to J J Maio.

35 records · Page 2Linked to original sources
PubMed1977

Subunit structure of chromatin and the organization of eukaryotic highly repetitive DNA: nucleosomal proteins associated with a highly repetitive mammalian DNA.

Component alpha DNA is a homogeneous, highly repetitive fraction that comprises nearly a quarter of the African green monkey (Cercopithecus aethiops) genome. By restriction enzyme analysis, it has a repeat periodicity of 176 +/- 4 nucleotide base pairs, corresponding closely with the length of DNA contained within a nucleosome. The sequence is organized into large blocks of constitutive heterochromatin. A method is described here for the isolation of intact polynucleosomal arrays containing only component alpha sequences. Isolated monkey nuclei are treated with EcoRI, which releases only component alpha nucleosomal arrays; the arrays are then fractionated and purified by sedimentation in sucrose gradients. The method permits a compositional analysis of the proteins associated with a constitutively repressed, heterochromatic sequence. The major differences in the proteins associated with component alpha nucleosomes that distinguish them from the bulk DNA nucleosomes are a decrease in the content of the H1 histones in the component alpha nucleosomes and a concomitant increase in the amount of certain nonhistone proteins. The specific observations are: (i) In the component alpha nucleosomes, 65-70% of the proteins were nonhistone proteins; this contrasts with the value, 40%, for nonhistone proteins associated with nucleosomes containing bulk DNA. (ii) The amount of H1 histone in chromatin containing predominantly bulk DNA was about 13.7%. However, the H1 histone was depleted and possibly absent in component alpha oligonucleosomes. (iii) Coincident with the decrease in the H1 histones and in the same molecular weight range (24,000-43,000), there appeared five minor nonhistone proteins. The minor, low-molecular-weight, nonhistone proteins were not detected in chromatin containing bulk DNA but they represented nearly 12% of the protein in component alpha nucleosomes. The resistance to salt extraction (0.6-2.0 M NaCl) indicates that the low-molecular-weight nonhistone proteins are tenaciously bound to the component alpha nucleosomes. In addition, a class of high-molecular-weight (>100,000) nonhistone proteins was enriched 5- or 6-fold in component alpha oligonucleosomes. The relative amounts of the nucleosome core histones were not changed.

Cell Line↗
PubMedDate not supplied

Transcription of the KpnI families of long interspersed DNAs in human cells.

The mammalian genome contains a variety of interspersed repetitive sequences of unknown function. It has, however, been suggested that interspersed repetitive sequences and their RNA transcripts are involved in the coordinate regulation of gene expression. Two major families of interspersed sequences in primates are the so-called Alu and KpnI families. Members of the KpnI families range in length from 1.2 to over 6 kilobases (kb). They exist in generally clustered arrangements, in 6 X 10(4) to 10(5) copies per diploid genome. Something is known of the arrangements of KpnI family sequences near human structural genes, but there has been no information on transcription of the sequences. We report here that the KpnI sequences are transcribed in HeLa cells by RNA polymerase II into abundant and heterogeneous species of RNA. The transcripts range in length from about 200 bases to over 5 kb, and are found predominantly in the non-polyadenylated fraction of the nuclear RNA. Transcripts homologous to both of the complementary strands of the KpnI sequences are present, but with a strong bias towards one strand.

Base Sequence↗