I'm not sure about the use of RNAlater for DNA purposes, but have you investigated TRIzol? It's been historically used for DNA, RNA, and protein, and can be hybridized with column extraction methods depending on your downstream plans.

Sealed and colder storage environments are consistently preferable to warmer for nucleotide and protein storage, but RNAlater should safely store your samples at room temperature for a few days if things don't get too warm.

https://www.thermofisher.com/us/en/home/references/ambion-tech-support/rna-isolation/tech-notes/rnalater-faqs.html

Hi, thank you for your answer! I'n not that familiar with TRIzol either, but the thing is that RNAlater we already have from a different project so it would be easy to use. And it's not us doing the downstream either, we will send the cells. The people who we will send them to suggested RNAlater, but didn't seem to have a good explanation as to why they want that... And most protocols, manuals etc I found for RNAlater (including that faq) talk about RNA and just briefly mention DNA, which i guess is understandable with RNA being the primary focus of the product. But since RNA is preserved so well, it's safe to assume DNA is, too?

I am not well-versed in what chemistry RNAlater is based upon. I have used both it and TRIzol to lead into RNA extraction procedures, and they both have worked well in the respective studies. I know that TRIzol (and phenolic based extraction methods) tend to stabilize and collect all nucleotides (DNA and RNA) without discrimination until later steps. You are probably fine for DNA as long as you can trust the experience of your collaborators.  Always good to also check the chosen method of publications regarding your end-process, too.

FWIW, we have successfully performed PCR for a mitochondrial gene on DNA extracted from copepods preserved in RNAlater. However, we did not really assess the quality of the extraction or other details of the preservation . We kept copepods in the fridge with RNA later and weeks to months later, PCR results were similar to what we got with EtOH fixed copepods. Low bar perhaps (amplifying a single mtDNA gene), but it worked in that capacity.

According to their FAQ:

"It is also possible to extract both genomic DNA and total protein from samples stored in RNA later. RNA later will denature proteins, so it is only compatible with routine protein analyses such as Western blotting and 2D gel electrophoresis that do not require native protein. Note: RNAlater is not recommended for use with tissues that will be sectioned using a cryostat.

https://www.thermofisher.com/us/en/home/references/ambion-tech-support/rna-isolation/tech-notes/rnalater-faqs.html