NAT14

NAT14 (KLP1) is a nuclear sequence-specific DNA-binding transcription factor that activates target gene expression (PMID:10873651). It binds the coproporphyrinogen oxidase promoter regulatory element (CPRE, GGACTACAG) through a protein bearing a leucine-zipper-like structure and a Leu-X-X-Leu-Leu motif, and stimulates transcription from CPRE-containing promoters (PMID:10873651). The NAT14 gene is itself a cell-cycle-responsive transcriptional unit: its TATA-less promoter depends on a CRE element at -42 bound by c-Jun and ATF1/CREB1, and promoter activity is elevated in cycling versus quiescent cells (PMID:11779635). Beyond autonomous DNA binding, NAT14 acts within a trimeric transcriptional complex together with the micropeptide MOXI and c-Jun, where MOXI phosphorylation at T49 drives its nuclear translocation and complex assembly to enhance basal and TGF-β1-induced collagen I promoter activity, linking NAT14 to fibrotic gene expression (PMID:36804379). Despite its name, NAT14 does not possess aspartate N-acetyltransferase activity, in contrast to its paralog NAT8L (PMID:19807691).

1. 2000 Medium

   Established that NAT14/KLP1 is not merely a sequence-named protein but a functional sequence-specific transcription factor, defining its DNA target and activator role.

   Evidence Southwestern cDNA library screening, EMSA, and reporter assay identifying CPRE (GGACTACAG) binding and transcriptional activation in THP-1 cells

   PMID:10873651

   Open questions at the time

   • Genome-wide target repertoire beyond the CPRE element not defined
   • Structural basis of DNA recognition by the leucine-zipper-like motif not resolved
   • Single-lab characterization without independent replication
2. 2001 Medium

   Resolved how NAT14 expression is itself controlled, placing the gene downstream of CRE-binding factors and cell-cycle status.

   Evidence Genomic sequencing, promoter deletion/mutagenesis, reporter assays, and EMSA with c-Jun/ATF1/CREB1 in K562 cells

   PMID:11779635

   Open questions at the time

   • Functional consequence of cell-cycle-dependent NAT14 expression on downstream targets not demonstrated
   • Role of the E2F site and GC boxes not functionally dissected
3. 2009 Medium

   Excluded a presumptive enzymatic function, showing NAT14 lacks the aspartate N-acetyltransferase activity of its paralog and forcing its role to be understood through transcription rather than acetylation.

   Evidence Transfection in HEK-293T cells with enzymatic NAA-synthesis assay; negative for NAT14, positive for NAT8L

   PMID:19807691

   Open questions at the time

   • Negative result does not exclude acetyltransferase activity toward other substrates
   • No catalytic activity of any kind positively assigned to NAT14
4. 2023 Medium

   Extended NAT14 function from autonomous DNA binding to a defined multiprotein transcriptional module, linking it mechanistically to fibrotic gene programs.

   Evidence BiFC interaction assay, collagen I promoter reporter, MOXI T49A knockin mouse, antisense knockdown, and folic acid/UUO fibrosis models

   PMID:36804379

   Open questions at the time

   • Direct NAT14-c-Jun and NAT14-MOXI binding interfaces not mapped
   • Whether NAT14 contacts the collagen I promoter DNA directly within the complex not established
   • Single-lab study

• How NAT14's CPRE-binding activity, cell-cycle-regulated expression, and MOXI/c-Jun complex function integrate into a unified regulatory program remains unresolved.
• No structural model of NAT14 or its DNA-binding mode
• Genome-wide target genes and physiological output beyond collagen I unknown
• Mechanism connecting CPRE/heme-pathway regulation to fibrotic gene control not established