Using fluorescence in situ hybridization, we determined that the three rat PAP genes, and the related REG gene map in the same chromosome region, namely 4q33→q34. This rat chromosome region is thus homologous to the human 2p12 region, which also contains the PAP gene, the REG1A gene, and a REG-related gene (REGL).
Fermentative and respiratory yeast strains of genera Saccharomyces, Kluyveromyces, Pichia, Candida and Hansenula have been investigated for mitochondrial localization of Cu/Zn superoxide dismutase (SOD). Pure mitochondrial fractions were obtained and the specific activities of Cu/Zn and Mn SODs were measured in comparison with those in the corresponding cell-free extracts. The Cu/Zn SOD: Mn SOD ratio in mitochondria and crude extracts was calculated and was considered a specific characteristic of all tested strains. Electrophoretical visualization of SOD patterns provided evidence for possible migration of cytosolic Cu/Zn SOD to mitochondria. The characteristic Cu/Zn SOD profile in mitochondria of all tested strains suggested its ubiquity within the fermentative and respiratory yeasts.
Nucleolar matrix structures were obtained under different extraction conditions from highly purified isolated nucleoli. Their ultrastructural appearance, protein composition and capacity to bind rDNA preferentially were studied in a model binding system. A region spanning approximately 25 kb in the rat ribosomal gene locus was screened for DNA sites capable of specifically interacting with the proteins of the nucleolar matrix (MARs). Two such sites were identified: one is located on an EcoRV-KpnI fragment in the 5'-nontranscribed spacer region, between two repetitive elements and close to the transcription initiation site; the other MAR is on a PvuII-BamHI fragment located in the 3'-nontranscribed region, encompassing an element 85% homologous to a B2-sequence. The two MARs are located in regions rich in polypyrimidine/polypurine tracks and contain a few elements homologous to the consensus sequence for topoisomerase II. This indicates that the "attachment sites" for the ribosomal genes belong to the same class of sequences as the MARs attaching the chromosomal DNA to the nuclear matrix.
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