Expression Of RNA-binding Protein Sam68 Messenger RNA In Primary Hepatocellular Carcinoma And Corresponding Significance

ForewordDuring the cell's growth and differentiation, gene expression is strictly controlled in the phases of transcription, posttranscription and translation. Transcription modulation is the first step of gene expression control, which was deemed to the primary regulation machanism of gene expression. But along with more and more comprehension about posttranscription modulation machanism, it is found that posttranscription modulation had the same important effect as transcription modulation to the gene expression. When gene was transcripted from cell nucleus, the new-synthesized pre-mRNA or hnRNA become mature RNA through a series of responses such as add-cap, splice of pre-mRNA, compose poly-A et al. Then the mature mRNA was transport to cytoplasm. The RNA's location, translation, and metabolism were strictly controlled in cytoplasm. The modulation mechanism determined the kinds and quantity of final products of gene expression.In the course of posttranscription modulation, many proteins were involved, in which the most important ones were RNA-binding proteins. These proteins participated in every step of RNA's splice, transport, locaion and metabolism. Their abnormality of structure and function usually lead to diseases. In past several years, because of involving many biological process, including signal transduction, cell cycle regulation, tumor pression, RNA-binding protein become another new research hotspot in tumor prevention and cure domain.In known RNA-binding proteins, signal transduction and activation of RNA(STAR) proteins were most deeply researched. Sam68 is one of the delegates of STAR proteins, which molecular weight was 68 kDa, and is src-associated substrate during mitosis. It has the KH domain flanked by conserved sequences, which was the character of STAR proteins and required for RNA binding activity. In addition, sam68 has several proline-rich sequences that are thesites of protein-protein interactions with SH3 and WW domain-containing proteins. Sam68 also has a tyrosine-rich C-terminus that is the site of phosphorylation by tyrosine kinases. The association with SH3 domain proteins and the tyrosine phosphorylation of sam68 has been observed to negatively regulate its RNA binding activity. Since tyrosine phosphorylation is one of the most familiar regulation manners of signal transduction way, sam68 was thought to participate the signal transduction course, and regulate mRNA expression through its ability to interact with kinds of proteins and RNA targets, and then affect the cell's proliferation, differentiation and growth.Many research indicated that sam68 was nearly correlated to cell proliferation and tumorigenesis. Random homozygous knock out(RHKO) NIH3T3 cells were shown to express less than 25% of sam68 compared to wild-type levels,and these cells exhibited anchorage-independent growth, defective contact inhibition and formed metastic tumors in nude mice. These studies suggest that sam68 maybe a potential tumor suppress factor.Now reports on sam68 are limited in foreign research, and most were about sequence or structure analysis and corresponding ligands examination, and research on relativity between sam68 and malignant tumor was few. There is no report on sam68 expression in primary hepatocellular carcinoma in due form.Through this study, we firstly determined the expression of RNA-binding protein sam68 mRNA in human primary hepatocellular carcinoma, and offered academic base for further research on mechanism of STAR preteins.Materials and Methods20 cases of tumor tissues and corresponding near-tumor tissues of human primary hepatocellular carcinoma were collected. Total RNA was extracted from specimens using TRIzol one-step method, then the specimens were examined on quality. According foreign literatures, we design a pair of specific primers respectively for sam68 and P-actin. The cDNA was synthesized from 2 μg of total RNA using MMLV transcriptase with random hexamers. The cDNA was amplified with the PCR. The intending PCR products was longas 530bp for sam68 and 300bp for p-actin...