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The MO15 cell cycle kinase is associated with the TFIIH transcription-DNA repair factor
MONITOR
p~ry, jo.urnals:... A missense mutation of the endothelin.B receptor gene in multigenic Hirschsprung'sdisease E.G. PUFFENBERGERETA&
Cell79, 1257-1266
Targetedand natural(piebald-lethal) mutations of endothelin-Breceptor gene producemegacolon associated with spotted coat color in mice K. HOSODA if/' AL.
Cell 79, 1267-1276
Interaction of endothelin.3 with endothelin-Breceptor is essential for development of epidermal melanocytes and enteric neurons A.G. BAYNASHETAL.
Cell79, 1277-1285 Progenitors that migrate from the vertebrate neural crest produce several cell types, including melanocytes and cells of the peripheral nervous system. Two classical mouse mutations, piebald (s) and lethal-spotting (is) result in defects in both of these lineages. Mutations at either locus result in extensive unpigmented patches on the coat, and in aganglionic
Relationship of CDK.activating kinase andRNA polymerase II ETDkinase TFIIB/TFIIK W.J. FEAVER,J.Q. SVEJSTRUP,N.L. HENRY AND R.D. KORNBERG
Ce1179, 1103--1109
The MO15cell cycle kinase is associatedwith the TFImtranscription.DNA repair factor R. ROY ETAL.
Cell 79, 1093-1101 It is still only relatively recently that
we have come to appreciate the intimate relationship between transcription and DNA repair. A particularly striking reminder of this association is the growing list of components shared between the basal transcription factor complex TFIIH (also called BTF2 and factor b), and a multisubunit complex required for nucleotide
I
megacolon, which is often lethal. The similarity of this phenotype to Hirschsprung's disease (HSCR) in humans, and the mapping of a recessive form of the disease to a homologous chromosomal location, has suggested that piebald and HSCR are the result of mutations in homologous genes. Surprisingly, work on a family of vasoactive peptides, the endothelins, and their receptors has identified the genes causing all three mutant phenotypes. There are three endothelins, EDN1, 2 and 3, which bind to two receptors, EDNRA and EDNRB. Both receptors act in the smooth muscles of blood vessels to mediate vasoconstriction in response to the endothelins but both also have a wider tissue distribution. To study the function of the proteins, Yanagisawa and colleagues made mice with null mutations in either Edn3 or Ednrb. Homozygous Edn3-null mice were largely unpigmented and died at a few weeks of age of aganglionic megacolon. The Edn3 gene in mouse maps on chromosome 2, near to the location of Is and the two mutations fail to complement. Baynash et al. demonstrated that there is a missense mutation in the Edn3 gene of Is, substituting an arginine with tryptophan. This change prevents the processing of the EDN3
precursor molecule, and completely abolishes its activity. In an accompanying paper, Hosoda et al. made a mouse line that is null for the EDNRB receptor. The homozygous mutantts have a very similar phenotype; large unpigmented regions of the coat and aganglionic megacolon. Mapping suggests that EDNRB might be encoded at the s locus, and indeed complementation studies show that they are allelic. The original s mutation is milder than the Ednrb null mutation; the mice rarely have megacolon and have fairly extensive pigmentation. The s mutation does not eliminate EDNRB production, but results in a reduced amount of mRNA and protein. A more severe allele, piebaldlethal, on the other hand, is a deletion of the gene and produces no active protein. A large Mennonite pedigree has HSCR mapping near to human EDNRB. Sequencing shows that in this family the disease is usually associated with a tryptophan to cysteine mutation in the receptor that impairs its function. Not all individuals homozygous for the mutation have the disease, however, indicating that it is a multigenic disorder, in which the penetrance of the EDNRB mutation is modified by genes elsewhere in the genome.
excision repair (NER). These shared components include RAD3/ERCC2/XPD, NSSL2/ERCC3/XPB, TFB1 and SSL1. The involvement of these factors in both transcription and NER goes a long way to explain the heterogeneous phenotypes associated with human genetic disorders previously thought to affect only DNA repair. These two papers indicate that the plot of this story has taken a further twist, by providing evidence that a serine/threonine kinase of the Cdc2p/Cdc28p family is also a component of the TFIIH transcription factor. A TFIIH-associated kinase has for some time been known to exhibit specificity for the C-terminal repeat domain (CTD) of RNA polymerase II, an activity which may be important for the initiation of transcription. In human cells, Roy et al. report that the CTD kinase activity of TFIIH is conferred by MO15, a protein first identified as the catalytic subunit of cyclin dependent kinase activating kinase (CAK) that phosphorylates
and activates p33 cdk2 and p34 cdc2. Indeed, CAK activity was found to copurify with TFIIH. In yeast, Feaver et al. identify a close relative of MO15 (the product of the essential KIN28 gene) as responsible for the CTD-kinase activity associated with TFIIH and demonstrate that recombinant human CAK has CTD-kinase activity. These new findings point to an unexpectedly close relationship between transcription, NER and cell cycle control. CAK activity has previously been shown to require association between MO15 and a cyclin H partner. It is likely that cyclin H is also involved in TFIIH-associated CTD-kinase activity. In yeast, this role may be fulfilled by the product of the essential CCL1 gene that interacts genetically with KIN28 and is the closest yeast homologue of cyclin H. MO15/cyclin H and KIN28/CCL1 may be the first identified essential cdk-cyclin pairs involved in transcription, cell cycle control and DNA repair.
TIG APRIL 1995 VOL. 11 No. 4
130
p~ry, jo.urnals:... A missense mutation of the endothelin.B receptor gene in multigenic Hirschsprung'sdisease E.G. PUFFENBERGERETA&
Cell79, 1257-1266
Targetedand natural(piebald-lethal) mutations of endothelin-Breceptor gene producemegacolon associated with spotted coat color in mice K. HOSODA if/' AL.
Cell 79, 1267-1276
Interaction of endothelin.3 with endothelin-Breceptor is essential for development of epidermal melanocytes and enteric neurons A.G. BAYNASHETAL.
Cell79, 1277-1285 Progenitors that migrate from the vertebrate neural crest produce several cell types, including melanocytes and cells of the peripheral nervous system. Two classical mouse mutations, piebald (s) and lethal-spotting (is) result in defects in both of these lineages. Mutations at either locus result in extensive unpigmented patches on the coat, and in aganglionic
Relationship of CDK.activating kinase andRNA polymerase II ETDkinase TFIIB/TFIIK W.J. FEAVER,J.Q. SVEJSTRUP,N.L. HENRY AND R.D. KORNBERG
Ce1179, 1103--1109
The MO15cell cycle kinase is associatedwith the TFImtranscription.DNA repair factor R. ROY ETAL.
Cell 79, 1093-1101 It is still only relatively recently that
we have come to appreciate the intimate relationship between transcription and DNA repair. A particularly striking reminder of this association is the growing list of components shared between the basal transcription factor complex TFIIH (also called BTF2 and factor b), and a multisubunit complex required for nucleotide
I
megacolon, which is often lethal. The similarity of this phenotype to Hirschsprung's disease (HSCR) in humans, and the mapping of a recessive form of the disease to a homologous chromosomal location, has suggested that piebald and HSCR are the result of mutations in homologous genes. Surprisingly, work on a family of vasoactive peptides, the endothelins, and their receptors has identified the genes causing all three mutant phenotypes. There are three endothelins, EDN1, 2 and 3, which bind to two receptors, EDNRA and EDNRB. Both receptors act in the smooth muscles of blood vessels to mediate vasoconstriction in response to the endothelins but both also have a wider tissue distribution. To study the function of the proteins, Yanagisawa and colleagues made mice with null mutations in either Edn3 or Ednrb. Homozygous Edn3-null mice were largely unpigmented and died at a few weeks of age of aganglionic megacolon. The Edn3 gene in mouse maps on chromosome 2, near to the location of Is and the two mutations fail to complement. Baynash et al. demonstrated that there is a missense mutation in the Edn3 gene of Is, substituting an arginine with tryptophan. This change prevents the processing of the EDN3
precursor molecule, and completely abolishes its activity. In an accompanying paper, Hosoda et al. made a mouse line that is null for the EDNRB receptor. The homozygous mutantts have a very similar phenotype; large unpigmented regions of the coat and aganglionic megacolon. Mapping suggests that EDNRB might be encoded at the s locus, and indeed complementation studies show that they are allelic. The original s mutation is milder than the Ednrb null mutation; the mice rarely have megacolon and have fairly extensive pigmentation. The s mutation does not eliminate EDNRB production, but results in a reduced amount of mRNA and protein. A more severe allele, piebaldlethal, on the other hand, is a deletion of the gene and produces no active protein. A large Mennonite pedigree has HSCR mapping near to human EDNRB. Sequencing shows that in this family the disease is usually associated with a tryptophan to cysteine mutation in the receptor that impairs its function. Not all individuals homozygous for the mutation have the disease, however, indicating that it is a multigenic disorder, in which the penetrance of the EDNRB mutation is modified by genes elsewhere in the genome.
excision repair (NER). These shared components include RAD3/ERCC2/XPD, NSSL2/ERCC3/XPB, TFB1 and SSL1. The involvement of these factors in both transcription and NER goes a long way to explain the heterogeneous phenotypes associated with human genetic disorders previously thought to affect only DNA repair. These two papers indicate that the plot of this story has taken a further twist, by providing evidence that a serine/threonine kinase of the Cdc2p/Cdc28p family is also a component of the TFIIH transcription factor. A TFIIH-associated kinase has for some time been known to exhibit specificity for the C-terminal repeat domain (CTD) of RNA polymerase II, an activity which may be important for the initiation of transcription. In human cells, Roy et al. report that the CTD kinase activity of TFIIH is conferred by MO15, a protein first identified as the catalytic subunit of cyclin dependent kinase activating kinase (CAK) that phosphorylates
and activates p33 cdk2 and p34 cdc2. Indeed, CAK activity was found to copurify with TFIIH. In yeast, Feaver et al. identify a close relative of MO15 (the product of the essential KIN28 gene) as responsible for the CTD-kinase activity associated with TFIIH and demonstrate that recombinant human CAK has CTD-kinase activity. These new findings point to an unexpectedly close relationship between transcription, NER and cell cycle control. CAK activity has previously been shown to require association between MO15 and a cyclin H partner. It is likely that cyclin H is also involved in TFIIH-associated CTD-kinase activity. In yeast, this role may be fulfilled by the product of the essential CCL1 gene that interacts genetically with KIN28 and is the closest yeast homologue of cyclin H. MO15/cyclin H and KIN28/CCL1 may be the first identified essential cdk-cyclin pairs involved in transcription, cell cycle control and DNA repair.
TIG APRIL 1995 VOL. 11 No. 4
130