Transcription factor that either stimulates or represses gene transcription through binding of different DNA regulatory elements such as cAMP response element (CRE) (consensus: 5'-GTGACGT[AC][AG]-3'), ATF5-specific response element (ARE) (consensus: 5'-C[CT]TCT[CT]CCTT[AT]-3') but also the amino acid response element (AARE), present in many viral and cellular promoters. Critically involved, often in a cell type-dependent manner, in cell survival, proliferation, and differentiation. Its transcriptional activity is enhanced by CCND3 and slightly inhibited by CDK4 (By similarity) (PubMed:19531563, PubMed:21212266). Important regulator of the cerebral cortex formation, functions in cerebral cortical neuroprogenitor cells to maintain proliferation and to block differentiation into neurons. Must be down-regulated in order for such cells to exit the cycle and differentiate (By similarity) (PubMed:12805299). Participates in the pathways by which SHH promotes cerebellar granule neuron progenitor cells proliferation. Critical for survival of mature olfactory sensory neurons (OSN), directs expression of OSN-specific genes (By similarity). May be involved in osteogenic differentiation. Promotes cell proliferation and survival by inducing the expression of EGR1 sinergistically with ELK1. Once acetylated by EP300, binds to ARE sequences on target genes promoters, such as BCL2 and EGR1 (By similarity) (PubMed:21791614). Plays an anti-apoptotic role through the transcriptional regulation of BCL2, this function seems to be cell type-dependent (By similarity). Cooperates with NR1I3/CAR in the transcriptional activation of CYP2B6 in liver. In hepatic cells, represses CRE-dependent transcription and inhibits proliferation by blocking at G2/M phase. May act as a negative regulator of IL1B transduction pathway in liver. Upon IL1B stimulus, cooperates with NLK to activate the transactivation activity of C/EBP subfamily members. Besides its function of transcription factor, acts as a cofactor of CEBPB to activate CEBPA and promote adipocyte differentiation. Regulates centrosome dynamics in a cell-cycle- and centriole-age-dependent manner. Forms 9-foci symmetrical ring scaffold around the mother centriole to control centrosome function and the interaction between centrioles and pericentriolar material (By similarity). Binds DNA as a dimer. Interacts with PTP4A1/PRL-1 (By similarity). Interacts with CCND3, but not with CCND1 or CCND2. Interacts with HSPA1A or HSPA1B; the interaction protects ATF5 from degradation via proteasome-dependent and caspase-dependent processes. Interacts (via C-terminal region) with NPM1 (via C-terminal region); the interaction leads to loss of association between HSPA1A or HSPA1B and ATF5 and promotes ATF5 degradation via proteasome-dependent and caspase-dependent processes. Interacts with NLK; the interaction stabilizes ATF5 at the protein level in a kinase-independent manner. Interacts with alpha-tubulin, gamma-tubulin members TUBGCP2 and TUBGCP4, PCNT; the ATF5:PCNT:polyglutamylated tubulin (PGT) tripartite unites the mother centriole and the pericentriolar material (PCM) in the centrosome (By similarity). Interacts with CEBPB and EP300; EP300 is required for ATF5 and CEBPB interaction and DNA binding (By similarity) (PubMed:21791614). Actively transported to the centrosome and accumulated in the pericentriolar material (PCM) during G1 to M phase via a microtubule-dependent mechanism. During late telophase and cytokinesis, translocates from the centrosome to the midbody. Expressed in embryonic nasal epithelium, dorsal root, trigeminal ganglia, brain and liver. Within the brain, expression is highest in the ventricular zone and decreased in structures containing migrating and postmitotic neurons (at protein level). Down-regulated during neuronal differentiation. Down-regulated by pro-apoptotic stimuli (PubMed:21212266). Ubiquitinated by CDC34 and UBE2B in order to be degraded by the proteasome. Acetylated at Lys-29 by EP300, the acetylation enhances the interaction with CEBPB, DNA-binding and transactivation activity. Ubiquitinated by CDC34 and UBE2B in order to be degraded by the proteasome. Cisplatin inhibits ubiquitination and proteasome-mediated degradation by inhibiting the interaction with CDC34. Ubiquitination and degradation by the proteasome are inhibited by NLK in a kinase-independent manner. Phosphorylated by NLK, probably at Ser-92 and Ser-126. Belongs to the bZIP family.