[Expression and function of Ahi-1 gene in Jurkat cells]

This study was aimed to investigate the expression, protein localization and function of Ahi-1 gene and its encoding protein in Jurkat cells. The expression of Ahi-1 mRNA and protein were measured by Northern and Western blot respectively. The plasmid containing prototype Ahi-1 was constructed and transfected into Jurkat cells. The Jurkat-A and Jurkat-C cells which either over-expressed the prototype Ahi-1 or not were obtained by selection with G418. The proliferation of the cells was assayed by XTT. The colony formation potential of the leukemia cells was checked by semisolid agarose culture. The results showed that three different transcripts of Ahi-1 (6.5,4.2 and 2 kb) were expressed in peripheral blood lymphocytes (PBLs), Jurkat and HUT78 cells. Ahi-1 protein with 140 kD localized in the cytoplasm majorly while traceless in the nucleus of Jurkat cells and PBLs from normal donor. Ahi-1 protein with 120 kD could be detected in the nucleus fraction of PBLs. Very low level of Ahi-1 protein with 120 kD was expressed in Jurkat cells. Up-regulating expression of Ahi-1 protein with 140 kD in the nucleus was found in Jurkat cells after exposure to meisoindigo, cytarabine, homoharringtonine, methotrexate and etoposide, down-regulating expression of Ahi-1 with 140 kD in the cytoplasm was observed after treatment with meisoindigo. The growth and colony formation potential were inhibited in the Jurkat-A cells, as compared to Jurkat-C cells. Total c-myb and phosphorylated AKT protein were continuously expressed in the Jurkat-C and Jurkat-A cells at similar level, but more phosphorylated c-myb was observed in Jurkat-A cells. It is concluded that three different transcripts of Ahi-1 at 6.5, 4.2 and 2 kb are detected in Jurkat cells; the Ahi-1 protein with 140 kD majorly expresses in the cytoplasm fraction and exposure to multiple chemotherapeutic compounds increased its expression in nucleus fraction. Over-expression of exogenous Ahi-1 can not only inhibit the growth and colony formation potential of Jurkat cells, but also induce the phosphorylation of c-myb in Jurkat cells.