Yes, PageRank is one of the key ranking factors, according to an official statement from Google (cited below); as a matter of fact, PageRank is an algorithm on its own. Although Google stopped reporting this metric, it is still used internally. The original paper on PageRank can be found here. Matt Cutts also discussed one of the changes in the PageRank algorithm, to tackle “PageRank sculpting”.

“PageRank works by counting the number and quality of links to a page to determine a rough estimate of how important the website is. The underlying assumption is that more important websites are likely to receive more links from other websites.” source