Phosphatase Family FCP

Phosphatase Classification: FCP

The FCP family is named after subfamily FCP1. It contains five catalytically active families, and one inactive one (TIMM50). Four of the five catalytically active families show phosphatase activity toward the C-terminal domain (CTD) of RNA polymerase II (Pol II). The CTD, found only in eukaryotes, consists of tandem repeated heptapeptide segments usually of a consensus sequence YSPTSPS, and the different phosphorylation patterns that predominate at each stage of transcription recruit the appropriate set of mRNA-processing and histone-modifying factors. FCP1 and SCP have different preference over pSer2 and pSer5, which may be important for regulating phosphorylation patterns. See Phosphorylation of RNA polymerase II C-terminal domain.

FCP1

F-cell production 1 (FCP1) also called TFIIF-stimulated CTD phosphatase 1, prefers to dephosphorylate pSer2 of heptapeptide repeats at CTD of RNA polymerase II.

SCP

SCP is named after Small CTD (carboxy-terminal domain, RNA polymerase II, polypeptide A) phosphatase. This subfamily has three members in human, SCP1 (or CTDSP1), SCP2 (or CTDSP2), and SCP3 (or CTDSPL). The SCP1 prefers to dephosphorylate pSer5 at CTD, while FCP1 prefers pSer2.

Dullard

Dullard, is also known as CTDNEP1 (CTD nuclear envelope phosphatase 1). However, its known substrate is lipin rather than RNA polymerase II CTD. The kinase of yeast lipin, SMP2, is Cdc28/cdk1.

HSPC129

HSPC129 is also known as HSPC058, and CTDSPL2 (CTD small phosphatase like 2). It has not been well characterized, though in vitro assay showed its phosphatase activity toward CTD.

UBLCP1

UBLCP1 is named after Ubiquitin-like domain containing CTD phosphatase 1. It has not been well characterized. It has a N-terminal domain similar to ubiquitin. Its putative substrate is RNA polymerase II C-terminal domain.

TIMM50

TIMM50, translocase of inner mitochondrial membrane 50 homolog. Catalytically inactive.

DxDxT motif

The pattern of DxDxT motif are obtained from eight organisms, yeast, Monosiga, sponge, anemone, worm, fly, sea urchin, and human.

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Subfamily	Motif pattern	Note
FCP1	DLDQT
SCP	DLDET
Dullard	DLDET	Exceptionally, one of the three fly Dullards has DMDNT.
HSPC129	DLDET
UBLCP1	D[I|V]DYT
TIMM50	-	Not very conserved.