GMW: New research shows 35S CaMV promoter is active in some human intestinal cel

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GMW: New research shows 35S CaMV promoter is active in some

human intestinal cells

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Mon, 14 Nov 2005 14:24:53 GMT

 

 

 

 

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Title : 35S CaMV promoter is active in some human intestinal cells

Date : 13 November 2005

Contents: THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE

 

Dear Friends and colleagues,

 

RE: 35S CaMV promoter is active in some human intestinal cells

 

The 35S promoter of the cauliflower mosaic virus (CaMV) is a general,

strong plant promoter. It has been used to secure expression of the

transgene in most genetically engineered (GE) crop plants

commercialized so

far.

 

It has been claimed that the 35S promoter is plant-specific and would

not be active in mammalian cells, and hence would not pose risks linked

to the consumption of GE food and feed in the event that plant DNA

fragments are taken up from the mammalian gastrointestinal tract.

However,

this claim has not been supported by experimental data.

 

On the contrary, there have already been published reports indicating

that this assumption might be incorrect, for example, previous research

has indicated the potential of the 35S promoter to be active in

mammalian systems. More recently, direct evidence that the 35S

promoter is

active in mammalian cell cultures has been presented.

 

Of particular importance are the cells lining the intestinal wall,

given that the gastrointestinal tract will be the first site of

exposure to

GE food and feed.

 

In a recently published paper, scientists have demonstrated that the

35S CaMV promoter was able to drive the expression of two reporter genes

(gfp and luc) in the human cell line Caco-2, which share a number of

characteristics with human enterocytes (cells lining the intestinal

wall).

 

While the protein expression levels were modest compared to results

obtained with strong mammalian promoters, the significant observation

remains that the 35S CaMV promoter, generally assumed to be plant

specific,

initiated significant protein expression levels in host cells that

share important characteristics with those lining parts of the human

gastrointestinal tract.

 

These results, taken together with other published papers, leads the

scientists to conclude that the 35S CaMV promoter is capable of

initiating gene expression in some mammalian cell lines under a range of

different conditions and circumstances. Computer based searches further

indicate that transcriptional activation by the 35S promoter may be

stronger

in other human and animal cell types than those investigated so far.

 

This research clearly warrants further serious investigation, including

by in vivo means.

 

Whether there are GE food safety implications would be linked to the

process of foreign DNA uptake from the human gastrointestinal tract. The

uptake of food-derived DNA fragments from the intestines into the blood

stream and some organs has already been demonstrated in various animal

species and recently also in humans.

 

Given the potential for the 35S promoter to initiate gene expression in

some mammalian cells, if the intact 35S promoter is taken up, the

biological consequences are potentially great (for example, inappropriate

expression of genes may occur).

 

The abstract of the paper is attached.

 

With best wishes,

 

Lim Li Ching

Third World Network

121-S Jalan Utama

10450 Penang

Malaysia

Email: twnet

Website: www.biosafety-info.net and www.twnside.org.sg

 

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REF: Doc.TWN/Biosafety/2005/C

 

The 35S CaMV plant virus promoter is active in human enterocyte-like

cells

 

European Food Reseach and Technology (2005)

DOI 10.1007/s00217-005-0154-3

 

Marit R. Myhre (2, 4), Kristin A. Fenton (4), Julia Eggert (3), Kaare

M. Nielsen (3) and Terje Traavik (1, 2)

 

(1) GENOK-Norwegian Institute of Gene Ecology, Science Park, N-9294

Tromsø, Norway

(2) Department of Microbiology and Virology, Institute of Medical

Biology, University of Tromsø, N-9037 Tromso, Norway

(3) Department of Pharmacy, University of Tromsø, N-9037 Tromsø, Norway

(4) Both authors have contributed equally, University of Tromso, N-9037

Tromso, Norway

 

Received: 22 May 2005 Accepted: 5 September 2005 Published online: 20

October 2005

 

Abstract

The 35S cauliflower mosaic virus (CaMV) promoter is commonly used to

drive transgene expression in the genetically engineered (GE) crop plants

that have been commercialized so far. Whether, and how far, the 35S

promoter might be active in mammalian cells has been scientifically

unsettled and controversial. Very recently it was established that the

35S

promoter is transcriptionally active following transient reporter gene

transfections in continuous cell lines of human [J Biotechnol

103:197–202, 2003] and hamster ovary [Environ Biosafety Res 3:41–47,

2004]

fibroblasts. The initial exposure of a human organism to DNA from GE food

takes place in the gastrointestinal tract (GIT). Hence, we have now

investigated the promoter capacity of 35S in human enterocyte-like

cells. We

constructed expression vectors with 35S promoter inserted in front of

two reporter genes encoding firefly luciferase and green fluorescent

protein (GFP), respectively, and performed transient transfection

experiments in the human enterocyte-like cell line Caco-2. It was

demonstrated

that the 35S CaMV promoter was able to drive the expression of both

reporter genes to significant levels, although the protein expression

levels might seem modest compared to those obtained with the strong

promoters derived from human cytomegalo virus (hCMV) and simian virus 40

(SV40). Furthermore, computer-based searches of the 35S CaMV DNA

sequence for

putative mammalian transcription factor binding motifs gave a high

number of hits. Some of the identified motifs indicate that

transcriptional

activation by the 35S CaMV promoter may be stronger in other human and

animal cell types than in those investigated so far.

 

 

 

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