Detection of novel mRNA splice variants of human ING4 tumor suppressor gene.

Inhibitor of growth (ING)4, member of a gene family encoding potential tumor suppressors, is implicated as a repressor of angiogenesis and tumor growth and suppresses loss of contact inhibition in vitro. Here, we report that ING4 undergoes alternative splicing. Expression analysis identified novel ING4 spliced variant mRNAs encoding proteins devoid of different portions. The ING4 variants were detected in both normal and tumor tissues. The existence of ING4 variants was confirmed by several approaches, including reverse transcriptase-polymerase chain reaction, real-time PCR and in silico experiments. To investigate the functional consequences of alternative splicing the ING4 variant cDNAs were expressed in mammalian cells. Our studies indicated that (i) the ING4 variants do not differ from wild-type in their nuclear localization, interaction with p53 and association to HBO1 complex; and (ii) the ING4-DeltaEx6A variant, devoid of the C-terminal portion, loses the capability to inhibit NF-kappaB. On the whole our data suggest that alternative splicing could modulate the activity of ING4 tumor suppressor protein.