Worm Breeder's Gazette 12(5): 23 (February 1, 1993)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Sequence Specificity for Somatic Tc3 Integration

Henri G.A.M. van Luenen, Ronald H.A. Plasterk

Figure 1

The Netherlands Cancer Institute, Division of Molecular Biology,
Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands

Transposition of the Tc3 transposon has been detected in the high

hopper strain TR679 which was initially selected for increased

transposition of the related element Tc1 .Both Tc1 and Tc3 insert at

a TA dinucleotide. A consensus sequence around this TA dinucleotide

has been proposed for Tc1 insertions in the germ line (G A G/T A/G

T A C/T G/T T; Mori et al., 1988, Proc. Natl. Acad. Sci. USA 85:86t-

864; Eide and Anderson, 1988, Mol. Cel. Biol. 8:737-746); this

consensus sequences is based on the comparison of 16 Tc1

insertions. We have sequenced 96 independent somatic Tc3

insertions to determine the Tc3 integration consensus sequence.

This is part of an ongoing study in which we compare Tc1 and Tc3

integration site specificity and in which we investigate the

predictive value of the Tc1 integration consensus sequence

mentioned above.

In the previous WBG (WBG, 1992 12/4:15) we described a transgenic

strain in which we could induce the expression of Tc3 transposase in

somatic tissues. The transgenic strain was made in a Bristol N2

background in which no Tc3 transposition occurs. After induction,

frequent somatic Tc3 transposition events were observed, as

witnessed by the appearance of extrachromosomal Tc3 elements and

by insertions of Tc3 in a random gene (the gpa-2 gene). Insertions

were detected by two rounds of PCR with nested oligo's. To

determine the insertion sites, the PCR products were excised from

an agarose gel and sequenced according to Craxton (Methods: A

companion to methods in enzymology, 1991 3:20-26).

The distribution of Tc3 insertions in an 1 kbp region of gpa-2 is

depicted in the figure. Each small line on the X axis represents a TA

dinucleotide: a potential Tc3 insertion site. The vertical bars

represent the number of Tc3 insertions found at a specific TA


[See Figure]

From the distribution we conclude that Tc3 insertions are not

random. TA dinucleotides which are frequently used for integration

are not clustered or regularly spaced. Furthermore, the TA

dinucleotide with the most frequent Tc3 insertion (24/96) is

flanked by two TA dinucleotides which are used only 1/96 or 0/96

times. This suggests that the local rather than the regional

structure of the DNA facilitates insertions.

The alignment (according to the 5'-3' orientation of the gpa-2 gene)

of all the 96 insertion sites of Tc3 results in the consensus

sequence: A(40%)/T(44%) A(60%) A(49%)/C(41%) T A T(79%) T(70%)

A(44%)/T(53%). The consensus sequence is not very strict; it does

not resemble the Tc1 consensus sequence.

Figure 1