KL201 (KL201) is an isoform-selective modulator of Cryptochrome 1 (CRY1), stabilize CRY1 but not CRY2.
KL201 did not affect CKId, CKIa, or CK2 activities.
KL201 binds to CRY1 in overlap with FBXL3, a subunit of ubiquitin ligase complex.
KL201 also repressed mRNA levels of Per2 and another CLOCK-BMAL1 target gene Dbp in wildtype fibroblasts, and the repression appeared to be reduced in Cry1 knockout cells but not in Cry2 knockout cells.
KL201 lengthened the period of circadian rhythms (Log EC2h=-5.63) in cells and tissues.
