Is it acceptable to contact the PI for a research position, in addition to applying through the careers site? At my institution there's an on-site cancer research center. I applied to a lab through the center's careers page for the position Research Associate 1. Basically they took my resume, cover letter, personal info and there's a message in an automated system saying I'm currently being considered. I do meet the requirements for the position, but as for the hiring process they don't provide a way of contacting a hiring manager, HR, etc. (I've looked deep, there's nothing except a "we'll get back to you if we're interested"). 

I have the email for the PI of the lab, but I'm unsure if it's acceptable to contact him about the position. What would be acceptable to say?
Unless this is an extremely high-profile position likely to get thousands of applicants, I don't think there is any harm in dropping the PI a brief email (3 sentences!) informing them you've applied for their position, telling them how much you respect their work, and letting them know they can contact you if they need any additional information.  If their HR department is useless, the PI may ask you to send your cover letter &amp; CV.  But write the letter in such a way that the PI can easily ignore the letter (doesn't feel obliged to respond) if their HR department functions well.