Amino terminal, but not the carboxy terminal, sequences of tropomyosin-1 are essential for the induction of stress fiber assembly in neoplastic cells

The presence of aberrant cytoskeleton, arising from the downregulation of key cytoskeletal proteins such as tropomyosins (TMs), is a prominent feature of many malignant cells and is suggested to promote neoplastic growth. While our previous work demonstrated that tropomyosin-1 (TM1) promotes stress fiber assembly and suppresses malignant growth, the molecular basis of the anti-oncogenic effects of TM1 has not been determined. By employing chimeric TMs, here we demonstrate that the amino terminal portion of TM1, but not the carboxy terminal portion which contains the alternatively spliced exon-coded sequences, is essential for stress fiber assembly and suppression of malignant growth. These studies also indicate that the amino and carboxy termini of TM1 coordinately function to regulate microfilament organization during cytokinesis.