Molecular attribution and the hepatic SREBP1 isoform hierarchy: The sequence defines the experiment

This is the authors' abstract. We don't add key points for this paper.

SREBP1c occupies a central position in prevailing models of hepatic lipogenesis, whereas SREBP1a is commonly treated as the quantitatively less important hepatic isoform. That hierarchy has strong biological foundations, yet several influential observations change meaning when the underlying molecular identity is resolved. A prominent antisense intervention reported as selective SREBP1c inhibition targeted a sequence within the Srebf1a-specific 5′ architecture. Independent human studies used an assay under an SREBP1c designation that instead interrogates SREBP1a-class transcript architecture. Previous human liver and primary hepatocyte data show that SREBP1a is quantitatively substantial, is detectable as mature protein and contributes to endogenous lipogenic regulation. Genuine SREBP1c-specific evidence remains intact under the same sequence standard. Orthogonal evidence comes from a transactivation-interface inhibitor that preferentially affects SREBP1a transactivation domain activity. Finally, acute pan-SREBP1 silencing can suppress directly measured hepatic de novo lipogenesis by approximately 70%, yet that flux has not been quantitatively partitioned between SREBP1a and SREBP1c. Together, these observations suggest that the hepatic SREBP1 hierarchy may reflect both biology and the way that biology was experimentally attributed.