B737 flight crew reported moderate turbulence; altitude and speed deviations in cruise flight.

Narrative

At FL390 approaching the northern point of squall line that extended from Location A to Location B we asked for heading to avoid a segment of wisps extending above the overcast level; told to stand by. I had the FAs (Flight Attendant) take their jump seats because it looked bumpy ahead. FO queried again for a heading to avoid that area; FAs were now seated. Finally as we entered the wisps we wanted to avoid ATC gave us authorization. In that area now; we hit moderate turbulence combined with wing roll that disengaged the AP (Autopilot) and caused the aircraft to climb and set off the overspeed clacker. I hand flew and we topped out at just less than 395. I had pulled power partially back in response to the overspeed in the climb; but kept well enough power to keep them spooled. We descended back to 390 and had a bit of a struggle re-engaging AP; due to a pre-existing issue with the left IRU (Inertial Reference Unit); but eventually using CMD B on FOs side and got it on. We were by now east of the squall line with smooth air. No injuries or other issues; remaining flight uneventful other than a failure of the Auto Brakes on descent.