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Evidences for insulator activity of the 5′UTR of the Drosophila melanogaster LTR-retrotransposon ZAM


Insulators or chromatin boundary are DNA elements that organize the genome into discrete regulatory domains by limiting the actions of enhancers and silencers through a “positional-blocking mechanism”. The role of these sequences, both in modulation of the enhancers range of action (enhancer–promoter selectivity) and in the organization of the chromatin in functional domains, is emerging strongly in these last years. There is a great interest in identifying new insulators because deeper knowledge of these elements can help understand how cis-regulatory elements coordinate the expression of the target genes. However, while insulators are critical in gene regulation and genome functioning, only a few have been reported so far. Here, we describe a new insulator sequence that is located in the 5′UTR of the Drosophila retrotransposon ZAM. We have used an “enhancer–blocking assay” to test its effects on the activity of the enhancer in transiently transfected Drosophila S2R+ cell line. Moreover, we show that the new insulator is able to affect significantly the enhancer–promoter interaction in the human cell line HEK293. These results suggest the possibility of employing the ZAM insulator in gene transfer protocols from insects to mammals in order to counteract the transgene positional and genotoxic effects.

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Fig. 1
Fig. 2
Fig. 3



Heterochromatin protein 1


Untranslated region


Suppressor of Hairy-wing


Long terminal repeat


Matrix/scaffold attachment region


Gene reporter luciferase


TATA-box sequence of the human cytomegalovirus immediate early promoter

EA :

Enhancer sequence of the regulative region of beta-actin


The fragment obtained from the second exon of the yellow gene


Gene reporter enhanced GFP

EC :

Enhancer of human cytomegalovirus immediate early promoter


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We thank Prof. Ruggiero Caizzi, for the critical reviewing and helpful discussion during the preparation of the manuscript. This work was supported by “Progetti di Ateneo” 2008 to L.V.

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Correspondence to Luigi Viggiano.

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Communicated by G. Reuter.

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Minervini, C.F., Ruggieri, S., Traversa, M. et al. Evidences for insulator activity of the 5′UTR of the Drosophila melanogaster LTR-retrotransposon ZAM. Mol Genet Genomics 283, 503–509 (2010).

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  • Insulator
  • LTR-retrotransposon
  • Gene expression
  • Drosophila melanogaster