Pnt1

Pnt1, or Pointed-1, is a hypothetical gene introduced in genetics textbooks to illustrate how a transcription factor can be organized and regulated in a eukaryotic genome. In the standard example, the Pnt1 locus spans about 6 exons and encodes a nuclear protein of roughly 70-75 kDa. The protein contains an N-terminal regulatory region, a central DNA-binding domain, and a C-terminal activation domain, with no known enzymatic activity.

Expression of Pnt1 is described as developmentally regulated: it is broadly expressed early in embryogenesis with elevated levels in differentiating tissues. Transcriptional control is mediated by a proximal promoter and two enhancers that respond to signaling cues. Post-translational modifications, such as phosphorylation, modulate its DNA-binding affinity and interaction with coactivators.

Functionally, Pnt1 is depicted as a nodal point in a differentiation cascade. In the illustrative pathway, Pnt1 activates a set of differentiation genes while repressing proliferation-associated genes, depending on cellular context and partner factors. The activity is coordinated with other transcription factors through protein-protein interactions.

In educational analyses, Pnt1 has conserved motifs across several simulated species, implying functional constraints. While not corresponding to an actual gene, Pnt1 serves as a compact model for discussing gene structure, regulatory networks, and the interpretation of genomic data.