Cyclin box fold superfamily; The cyclin box is a protein binding domain that functions in cell-cycle and transcriptional control. It is about 100 amino acids in length, composed of five helices, and is present in cyclins, transcription initiation factor IIB (TFIIB), and retinoblastoma tumour suppressor protein (Rb). Cyclins consist of 8 classes of cell cycle regulators that function as regulatory subunits of cyclin-dependent kinases (CDKs), which are serine/threonine kinases. The catalytic activities of CDKs are modulated not only by their interactions with cyclins but also by CDK inhibitors (CKIs). CDKs, cyclins and CKIs play key roles in transcription, epigenetic regulation, metabolism, stem cell self-renewal, neuronal functions, and spermatogenesis. TFIIB is a transcription factor that binds the TATA box. Members in this superfamily contain one or two copies of the cyclin box.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*.
gi 124512714 237 KFIIILGKYLQLSFCTICIALYYMNKYNQKILKRKKNsiSYLIAGACIFLAWKLRE 292
Cdd:cd00043    4 DFIRRLCSKLGLPEEVLELAIELLDRFLSKGLLLGRS--PELIAAACLYLACKLEE 57

Cyclin box fold superfamily; The cyclin box is a protein binding domain that functions in cell-cycle and transcriptional control. It is about 100 amino acids in length, composed of five helices, and is present in cyclins, transcription initiation factor IIB (TFIIB), and retinoblastoma tumour suppressor protein (Rb). Cyclins consist of 8 classes of cell cycle regulators that function as regulatory subunits of cyclin-dependent kinases (CDKs), which are serine/threonine kinases. The catalytic activities of CDKs are modulated not only by their interactions with cyclins but also by CDK inhibitors (CKIs). CDKs, cyclins and CKIs play key roles in transcription, epigenetic regulation, metabolism, stem cell self-renewal, neuronal functions, and spermatogenesis. TFIIB is a transcription factor that binds the TATA box. Members in this superfamily contain one or two copies of the cyclin box.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*.
gi 124512714 237 KFIIILGKYLQLSFCTICIALYYMNKYNQKILKRKKNsiSYLIAGACIFLAWKLRE 292
Cdd:cd00043    4 DFIRRLCSKLGLPEEVLELAIELLDRFLSKGLLLGRS--PELIAAACLYLACKLEE 57

domain present in cyclins, TFIIB and Retinoblastoma; A helical domain present in cyclins and TFIIB (twice) and Retinoblastoma (once). A protein recognition domain functioning in cell-cycle and transcription control.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*....
gi 124512714   237 KFIIILGKYLQLSFCTICIALYYMNKY--NQKILKRKknsiSYLIAGACIFLAWKLRED 293
Cdd:smart00385   1 DFLRRVCKALNLDPETLNLAVNLLDRFlsDYKFLKYS----PSLIAAAALYLASKTEET 55

Cyclin box fold superfamily; The cyclin box is a protein binding domain that functions in cell-cycle and transcriptional control. It is about 100 amino acids in length, composed of five helices, and is present in cyclins, transcription initiation factor IIB (TFIIB), and retinoblastoma tumour suppressor protein (Rb). Cyclins consist of 8 classes of cell cycle regulators that function as regulatory subunits of cyclin-dependent kinases (CDKs), which are serine/threonine kinases. The catalytic activities of CDKs are modulated not only by their interactions with cyclins but also by CDK inhibitors (CKIs). CDKs, cyclins and CKIs play key roles in transcription, epigenetic regulation, metabolism, stem cell self-renewal, neuronal functions, and spermatogenesis. TFIIB is a transcription factor that binds the TATA box. Members in this superfamily contain one or two copies of the cyclin box.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*.
gi 124512714 237 KFIIILGKYLQLSFCTICIALYYMNKYNQKILKRKKNsiSYLIAGACIFLAWKLRE 292
Cdd:cd00043    4 DFIRRLCSKLGLPEEVLELAIELLDRFLSKGLLLGRS--PELIAAACLYLACKLEE 57

second cyclin box found in Schizosaccharomyces pombe cyclin C homolog 1 (pch1), Saccharomyces cerevisiae CTD kinase subunit 2 (ScCTK2), and similar proteins; Cyclin pch1 is essential for progression through the whole cell cycle. It is a homolog of cyclin T; it forms a heterodimer with its partner kinase, cyclin-dependent kinase 9 (CDK9), that can phosphorylate both the pol II C-terminal domain (CTD) and the CTD of transcription elongation factor Spt5. Yeast Cdk9/Pch1, with mRNA capping enzyme Pct1, may also form an elongation checkpoint for mRNA quality control. CTK2, also called CTD kinase subunit beta, CTDK-I subunit beta, or CTD kinase 38 kDa subunit, is the cyclin subunit of the CTDK-I complex, which hyperphosphorylates the C-terminal heptapeptide repeat domain (CTD) of the largest RNA polymerase II subunit. This group also includes yeast RNA polymerase II holoenzyme cyclin-like subunit, a component of the SRB8-11 complex, a regulatory module of the Mediator complex which is involved in regulation of basal and activated RNA polymerase II-dependent transcription. Members of this family contain two cyclin boxes. This model corresponds to the second one. The cyclin box is a protein binding domain.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|....*...
gi 124512714 636 DIYKTPLCLIFTPKEILITCIlkaYISLKLLSNQL-HIRSLSFQDFED 682
Cdd:cd20546   31 DSYRTPLCLLYPPHVIAAAAI---YLAAKLLGIDLeLSPNEKLNEWWE 75