Transcription profiling of C/EBP targets identifies Per2 as a gene implicated in myeloid leukemia

CCAAT/enhancer-binding proteins (C/EBPs) are a family of transcription factors that regulate cell growth and differentiation in numerous cell types. To identify novel C/EBP-target genes, we performed transcriptional profiling using inducible NIH 3T3 cell lines expressing 1 of 4 members of the C/EBP family. Functional analysis revealed a previously unknown link between C/EBP proteins and circadian clock genes. Our microarray data showed that the expression levels of 2 core components of the circadian network, Per2 and Rev-Erb alpha, were significantly altered by C/EBPs. Recent studies suggested that Per2 behaves as a tumor suppressor gene in mice. Therefore, we focused our additional studies on Per2. We showed that Per2 expression is up-regulated by C/EBP alpha and C/EBP epsilon. Per2 levels were reduced in lymphoma cell lines and in acute myeloid leukemia (AML) patient samples. In addition, we generated stable K562 cells that expressed an inducible Per2 gene. Induction of Per2 expression resulted in growth inhibition, cell cycle arrest, apoptosis, and loss of clonogenic ability. These results suggest that Per2 is a downstream C/EBP alpha-target gene involved in AML, and its disruption might be involved in initiation and/or progression of AML.