"He and others find that these mRNA's direct,in large part,the synthesis of histones, a class of proteins that bind to DNA. "
It seems to me that perhaps the main verb is "is" (mRNA is direct). But I don't see a connection like a preposition between "mRNA's direct" and "the synthesis of histone". Also, there is a "is" - "mRNA's ", so I assume direct couldn't be a verb.
I can understand there are a subject, a main verb, and a main object. Seems everything is in there. But this sentence still seems weird to me. Why is this sentence a complete sentence? "mRNA's direct the synthesis of histones" : Looks weird to me.
Source: https://science.sciencemag.org/content/206/4416/315 Or you may view the below screenshot if it can not be zoom in.