SAP1a

SAP1A is one of a family of proteins that contains a unique DNA binding domain termed the ETS domain.

Transcription

The transcriptional activation domain of SAP1a resides within the C-terminal region, the function of which may be impeded by the N-terminus. Several potential ERK consensus sites within the C-terminal region of SAP1a can modulate its transactivation efficacy, implicating that SAP1a is a direct target of ERKs.^[1]

Interactions

SAP1a has been shown to interact with the c-fos serum response element upon recruitment by the serum response factor.

SAP1a is a nuclear protein stimulating transcription via the c-fos serum response element, and additionally via an Ets binding site independently of the serum response factor.^[1]

Insulin activated the human INSIG2 promoter in a process mediated by phosphorylated SAP1a.^[2]

Sap1a is phosphorylated efficiently by ERKs but not by SAPK/JNKs. Serum response factor-dependent ternary complex formation by Sap1a is stimulated by ERK phosphorylation but not by SAPK/JNKs. Moreover, Sap1a-mediated transcription is activated by mitogenic signals but not by cell stress.^[3]

ELK1 and SAP1a have been shown to form ternary complexes with SRF on the serum response elements (SRE) located in the c-fos promoter. ELK1, SAPla, FLI1 and EWS-FLI1 are able to form ternary complexes with SRF on EGR1 SREs. In addition, ELK1 and SAP1a can also form quaternary complexes on the Egr1 SREI.^[4]

Clinical significance

SAP1a activation by ERK may play an important role in the transformation of extracellular stimuli into a nuclear response.^[1]