The main stream of biology today is the analysis of the molecular mech
anisms of major biological phenomena through studies of the genes gove
rning these processes and their protein products. An example is the pr
oblem of tumor metastasis which is extremely important both theoretica
lly and practically. Here we describe the data obtained on the detecti
on, cloning, structure and transcription control of the mts1 gene, tha
t encodes metastasin 1, a protein which seems to play an important rol
e in the control of metastasis in mouse tumors. In particular, the exp
eriments on tumor cell transfection with constructions containing eith
er a sense or antisense mts1 sequence under a strong promoter/enhancer
element show the direct dependence of the metastatic phenotype on the
expression of the mts1 gene at least in some systems. Gene mts1 encod
es a protein belonging to the family of Ca2+-binding proteins and may
be involved in the control of cell motility in different types of cell
s, such as macrophages and T-lymphocytes. The relationship between mts
1 and other genes up- and down-regulated in metastatic cells is discus
sed.