Transcriptional activator which activates the CDKN2A/ARF locus in response to Ras-Raf signaling, thereby promoting p53/TP53-dependent growth arrest (By similarity). Binds to the consensus sequence 5'-CCCG[GT]ATGT-3' (By similarity). Isoform 1 may cooperate with MYB to activate transcription of the ANPEP gene. Isoform 2 may antagonize transcriptional activation by isoform 1. Interacts with the D-type cyclins CCND1, CCND2 and CCND3. Interaction with D-type cyclins may modulate transcriptional activation by this protein. Expressed at relatively low levels in colonic mucosa, ovary, peripheral leukocytes, prostate and small intestine, and at higher levels in spleen, testis and thymus. Expressed in multiple regions of the brain and CNS including amygdala, caudate, corpus callosum, hippocampus, substantia nigra and subthalamic nucleus. Isoform 1 is the predominant isoform in monocytes, macrophages and neutrophils, isoform 2 is most strongly expressed in peripheral blood leukocytes and quiescent CD34 positive cells, and isoform 3 is expressed at low levels in all hematopoietic cell types. Expression is frequently reduced in non-small-cell lung carcinomas (NSCLC) due to hemizygous gene deletion, strongly suggesting that this locus is haploinsufficient for tumor suppression. Loss of this locus frequently occurs in tumors which retain wild-type CDKN2A/ARF and p53/TP53 loci. Hemizygous gene deletion has also been observed in leukemic blasts from patients with abnormalities of the long arm of chromosome 7. Isoform 2 expression is down-regulated during myeloid differentiation, while the expression of isoform 1 and isoform 3 remain constant. Phosphorylated by the cyclin-D2/CDK4, cyclin-D3/CDK4 and cyclin-D2/CDK6 complexes and to a lesser extent by the cyclin-D1/CDK4 complex. Belongs to the DMTF1 family. Wrong choice of frame.