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Identification of a novel transforming growth factor-beta (TGF-beta 5) mRNA in Xenopus laevis.
Kondaiah P
,
Sands MJ
,
Smith JM
,
Fields A
,
Roberts AB
,
Sporn MB
,
Melton DA
.
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A novel transforming growth factor-beta (TGF-beta) mRNA of about 3.0 kilobases, which encodes a putative protein of 382 amino acids, has been identified in amphibians by cDNA cloning. This mRNA, which we designate as TGF-beta 5, is developmentally regulated and highly expressed beginning at early neurula (stage 14) and in many adult tissues in Xenopus laevis. Following the first methionine, the putative precursor protein has a hydrophobic region, approximately 22 amino acids long, which probably represents a signal sequence, similar to that found in TGF-beta s 1-3. The precursor also has potential sites for glycosylation, integrin binding (RGD), and a tetrabasic amino acid (RKKR) site for potential cleavage of the precursor peptide to a biologically active protein. The putative mature protein consists of 112 amino acids with 9 cysteines and has 76, 66, 69, and 72% identity to TGF-beta s 1-4, respectively.
FIG. 1. A, description of clone XCB4
and the sequencing strategy. The
hatched region represents the precursor
protein, whereas the shaded area represents
the mature protein of 112 amino
acids. The sequencing strategy is depicted
by +. B, nucleotide and deduced
amino acid sequence of XC(34. Nucleotides
are numbered on the left side of the
sequence. Amino acids are numbered on
top of the sequence. The putative signal
peptide is marked with a double ouerline.
Three potential glycosylation sites are
represented by a single ouerline. The potential
integrin binding site (RGD), conserved
in all TGF-Bs, with the exception
of TGF-P2, is indicated by a split ouerline.
The putative tetrabasic cleavage
site is represented by a heavy bar. The
mature peptide of 112 amino acids is
shown as a boxed-in region. The potential
polyadenylation signals (AATAAA)
are underlined.
FIN:. 2. A, comparison of the amino acid sequences of TGF-ps l-
5. The sequences of TGF-Bs l-4 have been obtained from the published
reports (l-4). The respective TGF-0s are designated on the left
side of each line. Amino acids are numbered on top with respect to
the sequence of TGF-65. Amino acid residues conserved in all 5 TGF-
/fs are represented by a +. An asterisk (*) represents the cysteines
conserved in all five TGF+s. Underlines represent the potential Nlinked
glycosylation sites (NXS/T), and the potential integrin binding
sit,e (RGD) is shown by -+ +. R, comparison of the amino acid
sequences of the putative mature protein of TGF-05 and the putative
mature protein of Vgl (5). Respective proteins are indicated on the
left side of the lines. Amino acids numbered on top and at the bottom
correspond t.o the respective proteins. A â:â represents the conserved
amino acid.
IG.
3. A, Northern blots showing hybridization to RNA isolated
from various developmental stages of X. laeuis. Each lane contains
poly(A’) RNA from five embryo equivalents. The top panel shows
hybridization with “LP-labeled antisense TGF-05 RNA, the bottom
panel with “‘P-labeled antisense Vgl RNA. Size markers show that
the TGF-85 transcript is about 3.0 kb; the Vgl transcript is about 2.8
kb. B, Northern blot analysis showing hybridization of “‘P-labeled
TGF-45 cDNA to RNAs derived from various tissues of adult X.
laeuis and from XTC cells. Each lane contains 15 pg of total RNA,
except lane 6, which has 5 pg. RNAs were resolved in 1.2% agarose
gels containing 2.2 M formaldehyde in 0.04 M MOPS buffer (pH 7.0).
Respective tissues are labeled above each lane.
