Total Number Of Copies Research Articles

Localization of RNA polymerase in polytene chromosomes of Drosophila melanogaster.

RNA polymerase (RNA nucleotidyltransferase) B (or II) and histone H1 of Drosophila melanogster were localized on salivary gland polytene chromosomes using the indirect immunofluorescence technique. RNA polymerase B is present almost exclusively in puffs and interband regions, whereas histone H1 is found primarily in bands. The puff at region 3C, known to be transcriptionally active in larval salivary glands, gives a bright fluorescence with antibodies against RNA polymerase B. This fluorescence disappears after exposure of the larvae to 37 degrees for 45 min. The heat shock treatment results in a general reduction of fluorescence intensity with the appearance of brightly staining heat shock puffs. Heat-induced removal of RNA polymerase molecules from a puff does not immediately alter its morphology. We propose than an interband represents that fraction of the total number of gene copies in a band that are active, the inactive copies being present in a condensed form in the adjacent band. Large puffs would originate through the decondensation and activation of most or all gene copies in a band.

Copies of proteins L7 and L12 and heterogeneity of the large subunit of Escherichia coli ribosome

The total number of copies of protein L12 and its α- N-acetylated form L7 in Escherichia coli ribosome has been determined and is found to be four. The previously reported variation of L12 to L7 ratio in ribosomes during the growth cycle can now be analyzed in terms of changes in the pattern of heterogeneity of the large ribosomal subunit. There must exist in E. coli at least two, but a maximum of five, subspecies of the large subunit with regard to the L7 L12 content. The observed variation in L12 L7 ratio would reflect continuous changes in the relative abundance of these subspecies in vivo during the growth cycle.