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        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTRPHWFLLFGTTEEEIQEICIETLRLYTRKKPNYELLEKEVEK 84
Cdd:cd20592    28 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPNRPHWFLLFGATEEEIQEICITTLKLYTRKKPNYEFLEKEVEK 107

                          90
                  ....*....|....*.
gi 1907151451  85 RKVALQEAKLKAKGLN 100
Cdd:cd20592   108 RKVALQEAKLKAKGLN 123

second cyclin box found in cyclin-L1 (CCNL1) and similar proteins; CCNL1 is an L-type cyclin involved in the regulation of RNA polymerase II (pol II) transcription. It functions in association with cyclin-dependent kinases (CDKs). CCNL1 contains two cyclin boxes. This model corresponds to the second one. The cyclin box is a protein binding domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTRPHWFLLFGTTEEEIQEICIETLRLYTRKKPNYELLEKEVEK 84
Cdd:cd20592    28 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPNRPHWFLLFGATEEEIQEICITTLKLYTRKKPNYEFLEKEVEK 107

                          90
                  ....*....|....*.
gi 1907151451  85 RKVALQEAKLKAKGLN 100
Cdd:cd20592   108 RKVALQEAKLKAKGLN 123

Cdk activating kinase (CAK)/RNA polymerase II transcription initiation/nucleotide excision repair factor TFIIH/TFIIK, cyclin H subunit [Cell division and chromosome partitioning / Transcription / DNA replication, recombination, and repair];

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*....
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARAlqIPLPTRPHWFLLFGTT 53
Cdd:COG5333   175 KIINDALRTDLCLLYPPHIIALAALLIACEV--LGMPIIKLLDFVSYET 221

second cyclin box found in cyclin-L1 (CCNL1) and similar proteins; CCNL1 is an L-type cyclin involved in the regulation of RNA polymerase II (pol II) transcription. It functions in association with cyclin-dependent kinases (CDKs). CCNL1 contains two cyclin boxes. This model corresponds to the second one. The cyclin box is a protein binding domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTRPHWFLLFGTTEEEIQEICIETLRLYTRKKPNYELLEKEVEK 84
Cdd:cd20592    28 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPNRPHWFLLFGATEEEIQEICITTLKLYTRKKPNYEFLEKEVEK 107

                          90
                  ....*....|....*.
gi 1907151451  85 RKVALQEAKLKAKGLN 100
Cdd:cd20592   108 RKVALQEAKLKAKGLN 123

second cyclin box found in cyclin-L (CCNL) family; The CCNL family includes two cyclins, CCNL1 and CCNL2. CCNL1 is involved in regulation of RNA polymerase II (pol II) transcription. It functions in association with cyclin-dependent kinases (CDKs). CCNL2 is a novel RNA polymerase II-associated cyclin involved in pre-mRNA splicing. It may induce cell death, possibly by acting on the transcription and RNA processing of apoptosis-related factors. 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        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTRPHWFLLFGTTEEEIQEICIETLRLYTR 70
Cdd:cd20533    27 NYMNDSLRTDLCVRYPPEVIACACIYLAARELGIPLPLPPPWWELFDVSKEDIEEICLTILELYTR 92

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        50
                  ....*....|....*....|....*....|....*....|....*....|...
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTRPH-----WFLLFGT 52
Cdd:cd20546    27 AFLNDSYRTPLCLLYPPHVIAAAAIYLAAKLLGIDLELSPNeklneWWELFGV 79

second cyclin box found in Arabidopsis thaliana T-type cyclins (CycTs) and similar proteins; CycTs associate with their partner cyclin-dependent kinases (CDKs) to trigger their kinase activity. CycTs show high sequence similarity with metazoan cyclin-K (CCNK). CycTs contain two cyclin boxes. This model corresponds to the second one. The cyclin box is a protein binding domain.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPT--RPHWFLLFGTTEEEIQEICIETLRLY 68
Cdd:cd20588    27 NFVNDGLRTSLCLQFKPHHIAAGAIFLAAKFLKVKLPCdgRKVWWQEFDVTPRQLEEVSNQMLELY 92

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
                  ....*....|....*....|....*....|....*....
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARALQIPLPTR 43
Cdd:cd00043    25 ELLDRFLSKGLLLGRSPELIAAACLYLACKLEELPRTLK 63

second cyclin box found in cyclin-T (CCNT) family; The CCNT family includes two C-type cyclins, cyclin-T1 (CCNT1) and cyclin-T2 (CCNT2), both of which are regulatory subunits of the cyclin-dependent kinase pair (CDK9/cyclin-T) complex, also called positive transcription elongation factor B (P-TEFb), which is proposed to facilitate the transition from abortive to productive elongation by phosphorylating the CTD (C-terminal domain) of the large subunit of RNA polymerase II (RNA Pol II). Members in 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 1907151451   8 NDSLRTNVFVRFQPETIACACIYLAAR--ALQIPLPTR-PHWF 47
Cdd:cd20539    30 NSLHLTTFCLQYKPTVIACVCIHLACKwsNWEIPRSSEgKDWY 72

Cdk activating kinase (CAK)/RNA polymerase II transcription initiation/nucleotide excision repair factor TFIIH/TFIIK, cyclin H subunit [Cell division and chromosome partitioning / Transcription / DNA replication, recombination, and repair];

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*....
gi 1907151451   5 NYMNDSLRTNVFVRFQPETIACACIYLAARAlqIPLPTRPHWFLLFGTT 53
Cdd:COG5333   175 KIINDALRTDLCLLYPPHIIALAALLIACEV--LGMPIIKLLDFVSYET 221