HnRNP A1/A2 Proteins Assemble onto 7SK snRNA via Context Dependent Interactions

•7SK snRNA adopts two alternate conformers with differences localized to the SL2-3 region.•HnRNP A1 binds selectively to the SL3 domain of 7SK to induce local structural changes.•SL3 positions multiple hnRNP A1 binding sites within different stereochemical environments.•Four hnRNP A1 proteins bind with high affinity and specificity through the upper surface of SL3.•A model is proposed to interpret complex binding mechanisms by which hnRNP A1 assembles onto 7SK.