M-phase-specific PLK1-interacting protein (TTD non-photosensitive 1 protein) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that in

humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

is encoded by the MPLKIP

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

(previously known as C7orf11). Patients with an inherited defect in both alleles of the gene suffer from

trichothiodystrophy Trichothiodystrophy (TTD) is an autosomal recessive inherited disorder characterised by brittle hair and intellectual impairment. The word breaks down into ''tricho'' – "hair", '' thio'' – "sulphur", and ''dystrophy'' – "wasting away" or lit ...

(TTD), a disease hallmarked by brittle hair and nails and usually by developmental difficulties as well. One patient carries a

homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

deletion of the whole gene area, which indicates that the gene is not essential for embryonic development. TTD can be diagnosed by the presence of tigertail-striped patterns in hair visible under polarised light microscopy, or biochemically by a reduced Cys content of the hairs. Only a minority of the TTD cases carry a MPLKIP defect: more frequently, the gene

ERCC2 __NOTOC__ ERCC2, or XPD is a protein involved in transcription-coupled nucleotide excision repair. The XPD (ERCC2) gene encodes for a 2.3-kb mRNA containing 22 exons and 21 introns. The XPD protein contains 760 amino acids and is a polypeptide w ...

is mutated, which encodes a subunit of the protein complex TFIIH that is required for general transcription and for

nucleotide excision repair Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucle ...

of DNA damage.

References

Further reading