I would go to the GEO (gene expression omnibus) or SRA depositories to check if there are any such datasets available. These depositories contain much of the datasets linked to already published work, so another way to go would be to check for ChIP-Seq publication in you species of interest in Pubmed and then look in the publications if the datasets are available (should be, it is mandatory to deposit your datasets before publication in most journals) and where are they accessible.

Good luck in your search, Fabrice.

Thanks Fab, your suggestions are quite reasonable, i checked already in SRA, but the problem is that i didn't found any medicinal or my sps of interested. But i will surely go through with your sec option by publications.

Definitely do the literature search and dig for sources of data. Not only was the SRA at NCBI shut down for a period of time (budget limitations), but its requirements for submissions are such that not all data can be submitted or at least not readily nor easily done (and so many people simple do not do it as configuring their data to conform to submission requirements would be too time consuming and complicated). While submission of array data is pretty much required by most journals, many have no such requirement for sequence data since the databases have been in flux, and have struggled to accommodate all data and file types, so editors recognize it may be taken as too great an impediment to authors. So a lot of next gen sequence data is either hosted on individual institutional servers, personal PI sites, or only available upon request.

Finding a publicly available sequence data set can be a bit of treasure hunt honestly as in my experience, the few public repositories have only captured a small fraction of the next gen sequence data that has been published.

hi Michael,

I am completely agree with your all points. I have experience with your last point about to download publicly NGS data specially about Solid small RNA-seq.

anyway thanks for your time and your views

As long as you find a publication that used data that might be useful to you, don't hesitate to contact the author(s) about getting data. Unless it was proprietary corporate data of some sort, most people I know would be happy enough to share their published data. I've had people send me a hard drive and I've shipped it back with data they asked for that was not in a public database, and I've gotten data that same way from others. And nowadays, many people will have access to a dropbox, box.net, or some other cloud storage they can use temporarily for you to transfer large data files over - so there is almost always a way to share data once you know who to ask. Best of luck.