If you mean gene expression (amount of mRNA produced), the answer is no. If you mean gene expression (amount of protein produced), the 5'UTR length, melting temperature, and sequence elements all affect protein levels. In general there is an inverse relationship between 5'UTR complexity/melting temperature and translation. Here's a paper: http://www.ncbi.nlm.nih.gov/pubmed/16540693

150bp seems quite normal. This other paper has a nice plot of deltaG for all 5'UTRs, so if you want to calculate your 5'UTRs deltaG with mFold you can understand a bit more stong the secondary structure it is: http://www.pnas.org/content/suppl/2009/12/11/0909773106.DCSupplemental/0909773106SI.pdf

There's so many possibilities for winning/losing here (see the above answers), I think yer' just gonna' have ta' give it a go, /pray,  and see what happens. OTOH, if "failure is not an option", bite the bullet and go ahead and delete the 150bp.

Thank you everyone for the feedback, and the interesting papers, Mark. I think I'm just going to go for it and hope for the best.

Cheers!

Short answer: we do not know enough about promoters to predict what will happen. Much more hard work is needed.

it depends if this region has a binding site for TF or repressor that can affect the activity of the promoter.

My best guess is, if this region determines the nucleosomal landscape of the promoter there can be a competition between nucleosome and the TF, if this region is altered thereby influencing gene expression. The above answers are all valid, I agree with jean delete it .. 

I am curious to know if you did detect some gene expression with the 150 bp distance in between the promoter and ATG?

As I also want to test my Tol 2 dest vector which is of the same situation as yours, as I used the PME-MCS to clone in my fragment.

Will be glad to hear back