Quantitative Analyses of Cryptochrome-mBMAL1 Interactions MECHANISTIC INSIGHTS INTO THE TRANSCRIPTIO

The mammalian cryptochromes mCRY1 and mCRY2 act astranscriptional repressors within the 24-h transcription-trans-lationalfeedbackloopofthecircadianclock.TheC-terminaltailandaprecedingpredictedcoiledcoil(CC)ofthemCRYsaswellasthe C-terminal region of the transcription factor mBMAL1 areinvolved in transcriptional feedback repression. Here we show byfluorescencepolarizationandisothermaltitrationcalorimetrythatpurifiedmCRY1/2CCtailproteinsformstableheterodimericcom-plexes with two C-terminal mBMAL1 fragments. The longermBMAL1fragment(BMAL490)includesLys-537,whichisrhyth-micallyacetylatedbymCLOCK