NEW YORK (TheStreet) -- Investors who thought the Greek debt crisis was over got a rude reminder Wednesday as violent protests in Athens shook U.S. markets once again.

Stocks gave up small gains in the afternoon and closed lower for the first time in five sessions as Greece's Parliament voted on the latest bailout plan while protesters rioted outside. 

The S&P 500 was down 0.07%, the Dow Jones Industrial Average fell 0.02%, and the Nasdaq slid 0.12%.

Prime Minister Alexis Tsipras has proposed a 86 billion euros bailout in exchange for strict spending cuts including pensions. Greece's parliament convened for the vote at 3 p.m. EDT.

Crude oil tumbled on Wednesday afternoon after President Barack Obama detailed plans to secure an Iran nuclear deal in exchange for the easing of sanctions.

"There really are only two alternatives here: either the issue of Iran obtaining a nuclear weapon is resolved diplomatically through a negotiation or it's resolved through force, through war. Those are the options," Obama said in a press conference.

Commodity traders fear that once international sanctions against Iran are loosened, Iranian oil will flood a global market already facing a supply glut. West Texas Intermediate crude closed 3.3% lower at $51.41, its lowest closing level since April.

All 12 of the U.S. Federal Reserve's districts recorded economic growth from mid-May through June, according to the Beige Book, an anecdotal account of economic health in populous pockets across the country. The U.S. economy expanded at a "moderate" to "modest" pace over the monitored period with a labor market rebound particularly pronounced in human resources, construction and IT vocations.

Earlier, Yellen shared a sunny forecast for the U.S. economy, noting that the central bank would likely raise interest rates in 2015 if the recovery continues at its current pace. Yellen shared the remarks to the House Financial Services Committee during her semi-annual testimony.

"If the economy evolves as we expect, economic conditions likely would make it appropriate at some point this year to raise the federal funds rate target," Yellen wrote in prepared comments before her speech. "Our judgment about that will depend on unfolding economic developments and how they affect our forecasts."

U.S. crude inventories saw a decline of 4.3 billion barrels for the week ended July 10, according to the Energy Information Administration. Analysts had expected a decline of 1.8 million barrels. Crude prices continued to fall despite the faster-than-expected drop. West Texas Intermediate crude was down 1.5% to $52.23 a barrel.

Industrial production in the U.S. rose 0.3% in June, higher than expectations of a 0.2% increase. Capacity utilization increased to 78.4% from 78.2%.

U.S. producer prices rose 0.4% in June, a touch higher than a 0.3% growth rate expected by economists. The reading was slightly slower than a 0.5% increase recorded in May. Excluding volatile items, core producer prices rose 0.3%.

Guess? (GES) jumped 7% on news co-founder Paul Marciano was stepping down as CEO. Marciano has held the position, either as sole or co-CEO, since 1999. He will remain with the company as executive chairman and chief creative officer. The move was seen as a positive by analysts -- Jefferies reiterated a "hold" rating, Telsey Advisory Group upgraded to "market perform" and Wunderlick raised price targets.

Bank of America (BAC) jumped 3.3% after earnings of 45 cents a share beat analysts' estimates of 36 cents. The bank reported a 1.8% increase in revenue on growth in core loans and higher mortgage originations.

Yum! Brands (YUM) shares were down 3% after the restaurant chain owner reported its fourth consecutive quarter of shrinking sales. Earnings of 69 cents a share beat estimates by 7 cents, while revenue fell 3.1% to $3.11 billion. Same-store sales in China tumbled 10% in a continued fallout from a food scandal in the region last year.

Celgene (CELG) spiked 7.1% after the biopharmaceutical company agreed to acquire Receptos (RCPT) for $7.2B in cash, or $232 a share. The deal will strengthen Celgene's portfolio of inflammation and immunology treatments. Receptos shares added 11%.

LinkedIn (LNKD) added more than 2% after Barclays analysts upgraded the stock to "overweight" and increased price targets to $250 from $225. Barclays analyst Paul Vogel said shares could see an upside after the company reports its second quarter at the end of the month after expectations were reset with lowered guidance in April.