I deal with this question and situation every day. If we were printing it, I'd ask you to build the artwork at 100% size (4436mm x 1300mm) at 125 to 300 PPI (Pixels Per Inch).
Then I would suggest that you avoid using Photoshop for this job if at all possible, and instead provide vector artwork from something like Illustrator. As you've discovered, the files you want to make are gigantic as raster at that size and resolution.
However, since I don't think my company is the one printing your job, (just a guess!) I would suggest that you contact the actual print company and ask them for their Prepress or File Prep Guidelines.