It seems that human Wee1 migrates anomalously on SDS-PAGE, often appearing at a higher molecular weight than expected. This sometimes occurs with proteins, either because of an unusual amino acid composition (more positively charged side chains than average), or post-translational modifications (Wee1 is known to be phosphorylated), or an SDS- and heat-resistant structure.

In order to explain why Wee1 is sometimes seen at 95 kDa and sometimes at 72 kDa, we could propose that post-translational modifications vary depending upon the host cell, or that the precise methodology of SDS-PAGE affects how it migrates (boiled or not boiled, for example). The latter effect has been described for other proteins.

Different migration rates of Wee1 on SDS-PAGE depending on phosphorylation were observed in this paper:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3510014/