A mammalian cell contains approx 10−5 μg of RNA which consists mainly of rRNA and in smaller amounts of a variety of low-mol-wt RNA species. These RNAs are of
defined size and sequence. The ability to isolate clean, intact, and DNA-free RNA is a prerequisite in analyzing gene expression
and cloning genes. The regulation of gene expression, e.g., the analyses of detailed function of transcription factors, promoter
and enhancer sequences, and RNA synthesis and processing as well as the analyses of gene expression after transfer of genes
of interest into eukaryotic cells are common areas of investigation in molecular biology. Important for the study of regulation
of gene expression is the ability to isolate, analyze, and quantify RNA molecules, specifically mRNAs coding for proteins
of interest. Furthermore, RNA is needed in order to copy it into double-stranded DNA for cloning and production of a cDNA
library. The critical first step in the construction of a cDNA library is the efficient isolation of undegraded total RNA.
The major difficulty in RNA isolation is the presence of ribonucleases found in virtually all tissues and liberated either
during cell lysis or accidentally introduced in traces from other potential sources.
[Show abstract][Hide abstract] ABSTRACT: F10 and BL6 cells of B16 mouse melanoma cells are metastatic after intravenous injection, but only BL6 cells can metastasize to lungs after subcutaneous injection. Differences in gene expression between the two cell lines were examined, and a greater expression of the Sik-similar protein (Sik-SP) gene was found in BL6 cells. Structurally, Sik-SP belongs to the nucleolar Nop5/Sik family whose members play central roles in ribosome biogenesis; however, the function of Sik-SP has not been examined. Cytology with green fluorescent protein-fused proteins showed that Sik-SP was localized to the nucleolus. To examine whether Sik-SP is involved in ribosome biogenesis, two parameters were measured: magnitude of ribosomal RNA synthesis per nucleus and magnitude of protein production from the same amount of mRNA of an exogenous luciferase gene. Both values and, in addition, nucleolar size were larger in COS-7 monkey kidney cells overexpressing Sik-SP and BL6 cells than in mock-transfected COS-7 and F10 cells, respectively. Sik-SP seemed to promote ribosome biogenesis in the nucleolus. Furthermore, the expression of Sik-SP seemed to confer a greater cell growth response to serum, because such a response was greater in BL6 cells and F10 cells overexpressing Sik-SP than in untreated and mock-transfected F10 cells. Sik-SP may render melanoma cells more competent to survive through augmenting the activity of nucleolus.
American Journal Of Pathology 11/2001; 159(4):1363-74. DOI:10.1016/S0002-9440(10)62523-0 · 4.59 Impact Factor
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