title: The rat XC sarcoma cell line: ribosomal RNA gene amplification and banded karyotype.
abstract: Ribosomal RNA gene amplification has been demonstrated in the rat XC sarcoma cell line. Cells of this rat line have a fairly stable karyotype with several unusual features, which have been clarified by in situ hybridization, silver staining, and binding of antibodies to 5-methylcytosine. There are one or two tiny acrocentric chromosomes containing transcriptionally active 18S and 28S ribosomal RNA (rRNA) genes. The short arm of one chromosome No. 12 has been replaced by a GC-rich, C-band negative, differentially staining region (DSR) containing an increased number of rRNA genes; most of these are transcriptionally inactive and located in regions containing highly methylated DNA. The short are of a small chromosome, probably a No. 20, has been replaced by a GC-rich, C-band negative, homogeneously staining region (HSR) that presumably represents amplification of a DNA sequence other than the 18S and 28S rRNA coding sequences. The DNA in this HSR is not enriched in 5-methylcytosine and neither is that in the HSRs of methotrexate-resistant Syrian hamster cells.
mesh_terms: D000818:Animals; D002460:Cell Line; D002871:Chromosome Banding; D005784:Gene Amplification; D005796:Genes; D007621:Karyotyping; D012334:RNA, Neoplasm; D012335:RNA, Ribosomal; D051381:Rats; D012513:Sarcoma, Experimental / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D012334:RNA, Neoplasm; D012335:RNA, Ribosomal