Story highlights Obama-era DHS secretary Jeh Johnson met with congressional investigators this week

The House panel's most recent public hearing was last month: ex-CIA Director John Brennan

(CNN) Former Homeland Security Secretary Jeh Johnson will testify next Wednesday before the House intelligence committee in a public hearing, according to a congressional source.

Johnson, who was DHS secretary under President Barack Obama, is the latest high-profile witness to appear publicly in the dual congressional probes into Russia's election interference being conducted by the House and Senate intelligence committees.

Johnson met Tuesday with the leaders of the House intelligence Russia probe, Reps. Mike Conaway of Texas and Adam Schiff of California, and he was interviewed by Senate intelligence committee staff Monday.

"I'm here voluntarily to assist the House intelligence committee on a matter of great importance," the former DHS secretary said after Tuesday's meeting. "So I welcome the opportunity to do that to help strengthen our nation's cybersecurity."

The House and Senate intelligence committees are both conducting separate investigations into Russia's election meddling and possible contacts with the Trump campaign.