Biology Reference
In-Depth Information
Ancestor
MUC5ACB progenitor
MUC2/6 progenitor
?
( ) 1
( ) 11
( ) 16
( ) ~100
( ) r
( ) 11
( ) 11
( ) 17
( ) 11
( ) 21
s
MUC6
MUC2
MUC5AC
MUC5B
Figure 4.22. Hypothetical scheme for the evolution of the MUC6 , MUC2 , MUC5AC , and
MUC5B mucin genes from a common ancestor (redrawn from Desseyn et al ., 1998). Unique
domains flanking the tandem repeat arrays, conserved in each protein, are represented by
rectangular or square boxes. A triangle represents the Cys sub-domain. The repetitive
central domains are represented by the following symbols: circles (closed, empty and
hatched) for the 23 amino acid tandem repeats of MUC2 , the 8 amino acid tandem repeats
of MUC5AC , and the 29 amino acid tandem repeats of MUC5B . The oval represents the
irregular 16 amino acid tandem repeat polypeptide of MUC2 . Diamonds represent the
MUC5B R-end sub-domain type. t, r, and s denote unknown numbers of repeats.
1993). Examples of human genes encoding RNA-binding proteins include the 70
kDa nuclear ribonucleoprotein ( SNRP70 ; 19q13.3) gene, the heterogeneous
nuclear ribonuclear riboprotein A1 ( HNRPA1 ; 12q13.1) gene, the Arg/Ser-rich
splicing factor ( SFRS2 ; chromosome 17) gene, the poly(A) binding protein
( PABPL1 ; 3q22-q25, 12q13-q14, 13q12-q13) genes, and the NCL (2q12-qter) gene
which encodes nucleolin, a protein involved in the control of transcription of
rRNA genes and in the nucleocytoplasmic transport of ribosomal components.
Sulfatase genes. Sulfatases catalyze the hydrolysis of sulfate ester bonds in a
variety of substrates. Sulfatase genes have been described in lower eukaryotes and
comprise an evolutionarily conserved multigene family in human (Parenti et al .,
1997): arylsulfatase A ( ARSA ; 22q13), arylsulfatase B ( ARSB ; 5q11-q14), arylsul-
fatase D ( ARSD ; Xp22.3), arylsulfatase E ( ARSE ; Xp22.3), arylsulfatase F
( ARSF ; Xp22.3) proximal to the pseudoautosomal boundary, steroid sulfatase
( STS ; Xp22.3) 4 Mb distant from the ARSD / ARSE / ARSF cluster, iduronate-
2-sulfatase ( IDS ; Xq27-28), galactose 6-sulfatase ( GALNS ; 16q24) and
glucosamine 6-sulfatase ( GNS ; 12q14). The chromosomally dispersed sulfatase
genes exhibit a relatively low degree of sequence identity consistent with these
genes having emerged comparatively early during evolution. By contrast, the
four genes located at Xp22.3, within the pseudoautosomal region, are more simi-
lar in sequence, share a very similar exon-intron organization and possess homo-
logues on the Y chromosome (Meroni et al ., 1996), consistent with duplication
events that occurred before the X and Y copies of these genes started to diverge
(i.e. while they were still pseudoautosomal).
 
 
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