MEXICO CITY (Reuters) - Mexico's President Enrique Pena Nieto on Tuesday nominated his third attorney general in four years in a plan that would move the incumbent to an anti-corruption post vacant since July.

Pena Nieto put forward Raul Cervantes, a senator from the ruling Institutional Revolutionary Party (PRI) to replace Arely Gomez, another PRI senator who assumed the job during a period of turmoil in March 2015.

Her tenure was overshadowed by criticism of the government’s investigation of the disappearances of 43 trainee students in southwest Mexico in September 2014, a scandal that dogged her predecessor, Jesus Murillo.

Under Murillo, the government found the 43 had been abducted by corrupt police and handed over to members of a drug cartel, who murdered and incinerated them in the belief that the students’ college had been infiltrated by a rival gang.

However, international experts picked holes in the official version and questions about the case remain unanswered. Only the remains of one of the 43 have been identified.

Gomez also had to contend with the July 2015 escape from a maximum security prison of drug lord Joaquin “El Chapo” Guzman before his recapture this January.

Announcing the changes in a statement, the president’s office said it had proposed Gomez should serve as head of the Public Administration Ministry, the government's main anti-corruption auditor.

Both appointments must be ratified by the Senate.

    The shake-up comes as Pena Nieto’s government faces growing pressure to curb rising gang violence and allegations of political corruption that helped consign the PRI to a historic defeat in regional elections in June.

Pena Nieto took office in December 2012 and has just over two years left to serve.

(Reporting by Natalie Schachar and Dave Graham; editing by Robert Birsel)