Sort the following events to reflect the normal order in which they occur in G-protein-coupled receptor signaling leading to transcription of genes with cAMP response elements. Your answer would be a four-letter string composed of letters A to E only, e.g. ACBD.
(A) Binding of CREB to PKA
(B) Binding of cAMP to PKA
(C) Dissociation of PKA into catalytic and regulatory subunits
(D) Activation of adenylyl cyclase