Si-1基因是本实验室发现的一个基因，该基因在细胞生长停止时表达，在细胞生长旺盛时不表达；在30天龄小鼠睾丸组织中特异表达。将已获得的部分序列与基因数据库序列比较没有明显的相似性，所以这是一个新的细胞周期调控相关基因。本研究将克隆该基因的全长序列并确定它在细胞周期调控中的作用。这一研究对探讨细胞生长和分化机制有重要意义。

Comparing the gene expression of serum starving cell with normal incubation cell, we discovered a fragment of gene which expressed higher level in serum starving cells than serum incudation cells. According to the gene which expression was inhibited by serum, it was named serum inhibite gene(abbreviated Si-1 gene).This project would clone the full cDNA sequence of this gene and characte it role in cell cycle. During this project process, the full cDNA sequence of Si-1 was cloned. This gene contain 5429 bp , which coded 792 amine acid ,local in human chromosome 2 and consist of 21 exons. This gene was identified as a cell cycle control gene by comparing serum starving cells with serum medium and transfection experiment,and that it was not amplified by using PCR in 55.5% brain tumor tissue and 50% in Hepatocellular Carcinomas tissue，which suggested that there are high deletion or mutation of this gene in brain tumor and Hepatocellular Carcinomas and related closely with tumorgenerate . It is first research that the structure and function of this gene were sdudied.