Robert Pattinson and Sean Penn are circling Fox 2000′s Depression-era drama “Water for Elephants.”Reese Witherspoon has already boarded to the film, which will be directed by Francis Lawrence. Scribe Richard LaGravenese is adapting for the bigscreen. Based on Sara Gruen’s best-selling historical tome of the same name, story centers on a Cornell U. veterinary student who leaves his studies after his parents are killed and joins up with the Benzini Brothers Most Spectacular Show on Earth, working as a vet for the circus. Witherspoon will play Marlena, the beautiful equestrian star married to August (Penn), the charismatic but twisted animal trainer. Studio, which is eyeing a June start date, wouldn’t confirm details of the project. Gil Netter, Erwin Stoff and Andrew Tennenbaum are producing. “Twilight” star Pattinson has been on every studio’s wish list. His deal is expected to close. Penn, who is in Haiti on a humanitarian mission, is the bigger question mark. He has an offer from the studio but is still mulling the role.